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Srabionyan, V., Heinz, M., Kaptelinin, S., Avakyan, L., Sukharina, G., Skidanenko, A., Pryadchenko, V., Abdulvakhidov, K., Mikheykin, A., Durymanov, V., Meinertz, J., Ihlemann, J., Dubiel, M., Bugaev, L. Effect of thermal post-treatment on surface plasmon resonance characteristics of gold nanoparticles formed in glass by UV laser irradiation 2019 J. Alloys Compd.
Vol. 803, pp. 354 
article DOI URL 
Abstract: Effects of thermal post treatment and of thickness of the initial gold film coated the silicate glass surface, on localized surface plasmon resonance (SPR) of gold nanoparticles formed in glass by UV laser irradiation were studied to develop effective technique for production of gold nanoparticles and their arrays with required and stable characteristics of SPR. Optical spectra of the obtained Au/glass samples showed that SPR of gold nanoparticles formed by irradiation of glasses sputter coated with gold films of thickness 6–10 nm depends of T-treatment, while irradiation of glass coated with gold film ∼70 nm leads to SPR stable of temperature. The origin of such dependences was studied by the structural analysis of gold nanoparticles in Au/glass samples before and after thermal treatment using XRD, EXAFS methods, TEM-EDX images and direct calculations of optical spectra. It was revealed that the changes or stability of SPR parameters under thermal post-treatment of Au/glass samples depend respectively of the presence or absence of tin atoms in the near-surface region (shell) of the gold particles. Thus, if tin atoms are presented in the shell of gold particles (as in “as prepared” Au/glass samples initially coated with gold films of 6–10 nm) then the leave of tin atoms from the particles volume during the heating leads to partial dissolution of the particles shell and consequently, to decreasing of the particles size, which in turn leads to the observed changes in SPR. The most probable explanation of the presence of tin atoms in the shell of gold particles formed by irradiation of samples initially coated with gold films of thickness 6–10 nm and their absence in the case of sample with film ∼70 nm was proposed, basing on the difference in the effects of the first laser pulse actions on these films on the tin-bath side of the glass samples. The sizes of coherent scattering region in gold nanoparticles before and after thermal treatment of Au/glass samples were determined and the dependence of these sizes upon the thickness of the gold film coating the samples surface before laser irradiation was revealed.
BibTeX:
@article{Srabionyan2019,
author = {Vasiliy, Srabionyan and Heinz, Maximilian and Kaptelinin, Sviatoslav Yu and Avakyan, Leon A. and Sukharina, Galina B. and Skidanenko, Anna V. and Pryadchenko, VasiliyV. and Abdulvakhidov, Kamal G. and Mikheykin, AlexeyS. and Durymanov, VeniaminA. and Meinertz, Jörg and Ihlemann, Juergen and Dubiel, Manfred and Bugaev, Lusegen A.},
doi = {10.1016/j.jallcom.2019.06.263},
issn = {0925-8388},
journal = {J. Alloys Compd.},
pages = {354–363},
title = {Effect of thermal post-treatment on surface plasmon resonance characteristics of gold nanoparticles formed in glass by UV laser irradiation},
url = {http://www.sciencedirect.com/science/article/pii/S0925838819323539},
volume = {803},
year = {2019}
}
Avakyan, L.A., Paramonova, E.V., Coutinho, J., Öberg, S., Bystrov, V.S. and Bugaev, L.A. Optoelectronics and defect levels in hydroxyapatite by first-principles 2018 J. Chem. Phys.
Vol. 148(15), pp. 154706 
article DOI URL 
Abstract: Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material (e.g., in photo-catalysis) depend on how well we understand its fundamental properties. Among the ones that are either unknown or not known accurately, we have the electronic band structure and all that relates to it, including the bandgap width. We employ state-of-the-art methodologies, including density hybrid-functional theory and many-body perturbation theory within the dynamically screened single-particle Green’s function approximation, to look at the optoelectronic properties of HAp. These methods are also applied to the calculation of defect levels. We find that the use of a mix of (semi-)local and exact exchange in the exchange-correlation functional brings a drastic improvement to the band structure. Important side effects include improvements in the description of dielectric and optical properties not only involving conduction band (excited) states but also the valence. We find that the highly dispersive conduction band bottom of HAp originates from anti-bonding σ* states along the ⋯OH–OH–⋯ infinite chain, suggesting the formation of a conductive 1D-ice phase. The choice of the exchange-correlation treatment to the calculation of defect levels was also investigated by using the OH-vacancy as a testing model. We find that donor and acceptor transitions obtained within semi-local density functional theory (DFT) differ from those of hybrid-DFT by almost 2 eV. Such a large discrepancy emphasizes the importance of using a high-quality description of the electron-electron interactions in the calculation of electronic and optical transitions of defects in HAp.
BibTeX:
@article{CoutinhoHAp2018,
  author = {Leon A. Avakyan and Ekaterina V. Paramonova and José Coutinho and Sven Öberg and Vladimir S. Bystrov and Lusegen A. Bugaev},
  title = {Optoelectronics and defect levels in hydroxyapatite by first-principles},
  journal = {J. Chem. Phys.},
  year = {2018},
  volume = {148},
  number = {15},
  pages = {154706},
  url = {https://doi.org/10.1063/1.5025329},
  doi = {http://doi.org/10.1063/1.5025329}
}
Heinz, M., Srabionyan, V., Avakyan, L., Bugaev, A., Skidanenko, A.V., Pryadchenko, V., Ihlemann, J., Meinertz, J., Patzig, C., Dubiel, M. and Bugaev, L. Formation and implantation of gold nanoparticles by ArF-excimer laser irradiation of gold-coated float glass 2018 J. Alloys Compd.
Vol. 736(5), pp. 152-162 
article DOI URL 
Abstract: Highlights

• Arrays of plasmonic Au NPs in glass were produced using UV-laser technique.
• Dependence of SPR in Au NPs upon the number of laser pulses and fluence is obtained.
• Laser implantation of Au NPs in glass is supported by enhanced absorption of tin ions.
• Structural characterization of the formed Au NPs was performed by TEM, XRD, EXAFS.
• Optical extinction spectra of arrays of Au NPs in glass were described by MSTM method.

Abstract

To develop a technique for the production of submicron line patterns and directed arrays of plasmonic nanoparticles, the generation and implantation of gold nanoparticles into float glass surfaces was studied by means of ArF-excimer laser irradiation (193 nm) below the ablation threshold of the glass which was sputter coated with a gold layer with a thickness of 70 nm. The formation of gold particles was confirmed by the characteristic surface plasmon resonance (SPR) peak at ∼550 nm. The intensity of the SPR peak of gold particles embedded in the glass matrix increases with the number of applied laser pulses, indicating a different degree of implantation of the gold nanoparticles into the glass surface. It was revealed that the laser implantation of the generated gold particles into the glass is supported on the tin-bath side by the enhanced absorption of tin ions. The dependences of SPR parameters upon the number of laser pulses at different fluences were obtained. Using the methods of X-ray diffraction and extended X-ray absorption fine structure, the mean size of implanted gold particles was estimated at 15–20 nm. This particle size was confirmed by analytical (scanning) transmission electron microscopy, but a small fraction of single particles with a size of ∼50 nm have also been observed. The particles arrangement was further examined by the fitting of experimental optical extinction spectra, varying the particles sizes and interparticle distances within the direct calculations of spectra by the multi-spheres T-matrix method, considering the possible agglomerations of particles. The applied experimental technique provides the creation of arrays of gold nanoparticles in the near-surface region of the glass, which can be used as the substrates or nuclei in the glass for producing bimetallic nanoparticles with gold as the core and SPR characteristics varied in a wide range of visual wavelengths.

BibTeX:
@article{Heinz2018,
  author = {Heinz, M. and Srabionyan, V.V. and Avakyan, L.A. and Bugaev, A.L. and Skidanenko A.V. and Pryadchenko, V.V. and Ihlemann, J. and Meinertz, J. and Patzig, C. and Dubiel, M. and Bugaev, L.A.},
  title = {Formation and implantation of gold nanoparticles by ArF-excimer laser irradiation of gold-coated float glass},
  journal = {J. Alloys Compd.},
  year = {2018},
  volume = {736},
  number = {5},
  pages = {152-162},
  url = {http://www.sciencedirect.com/science/article/pii/S0925838817338793},
  doi = {http://doi.org/10.1016/j.jallcom.2017.11.122}
}
Manukyan, A.S., Avakyan, L.A., Elsukova, A.E., Zubavichus, Y.V., Sulyanov, S.N., Mirzakhanyan, A.A., Kolpacheva, N.A., Spasova, M., Kocharian, A.N., Farle, M., Bugaev, L.A. and Sharoyan, E.G. Formation of nickel nanoparticles and magnetic matrix in nickel phthalocyanine by doping with potassium 2018 Mater. Chem. Phys.
Vol. 214, pp. 564-571 
article DOI URL 
Abstract: A method for synthesis of nickel nanoparticles in a magnetic nickel phthalocyanine anions matrix has been developed. The method is based on intercalation of potassium atoms to the nickel phthalocyanine (NiPc) polycrystalline powder at 300 °C. The structure of (K2NiPc) was investigated by using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) spectroscopes. Magnetic properties were studied by SQUID magnetometry and magnetic resonances methods. It is revealed that the resultant compound contains of 1 wt% Ni nanoparticles with the average size of 15 nm. The measured values of the magnetization and absorption of the ferromagnetic resonance considerably exceed the magnetism which can be attributed to metallic Ni nanoparticles. The obtained results indicate the presence of room temperature molecular ferromagnetism caused by anionic molecules of NiPc.
BibTeX:
@article{Manukyan2018,
  author = {Aram S. Manukyan and Leon A. Avakyan and Anna E. Elsukova and Yan V. Zubavichus and Sergey N. Sulyanov and Armen A. Mirzakhanyan and Natalia A. Kolpacheva and Marina Spasova and Armen N. Kocharian and Michael Farle and Lusegen A. Bugaev and Eduard G. Sharoyan},
  title = {Formation of nickel nanoparticles and magnetic matrix in nickel phthalocyanine by doping with potassium},
  journal = {Mater. Chem. Phys.},
  year = {2018},
  volume = {214},
  pages = {564-571},
  url = {https://www.sciencedirect.com/science/article/pii/S0254058418303377},
  doi = {http://doi.org/10.1016/j.matchemphys.2018.04.068}
}
Pryadchenko, V.V., Belenov, S.V., Shemet, D.B., Srabionyan, V.V., Avakyan, L.A., Volochaev, V.A., Mikheykin, A.S., Bdoyan, K.E., Zizak, I., Guterman, V.E. and Bugaev, L.A. Effect of Thermal Treatment on the Atomic Structure and Electrochemical Characteristics of Bimetallic PtCu Core–Shell Nanoparticles in PtCu/C Electrocatalysts 2018 J. Phys. Chem. C
Vol. 122(30), pp. 17199-17210 
article DOI URL 
Abstract: Supported PtCu/C electrocatalysts containing core–shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu2+ and Pt(IV) in a carbon suspension, prepared on the basis of ethylene glycol–water solvent, and then treated at different temperatures in the range from 250 to 350 °C. The structural characterization of “as-prepared” PtCu nanoparticles and of those obtained after the thermal treatments was performed by transmission electron microscopy, X-ray diffraction, and Pt L3- and Cu K-edge extended X-ray absorption fine structure spectroscopy. The atomic cluster models of PtCu nanoparticles before and after the thermal treatment, reflecting the character of the components’ distribution, were generated. The electrochemical performance of the obtained PtCu/C electrocatalysts in oxygen reduction reaction was studied by cycling and linear voltammetry.
BibTeX:
@article{Pryadchenko2018,
  author = {Pryadchenko, Vasiliy V. and Belenov, Sergey V. and Shemet, Darya B. and Srabionyan, Vasiliy V. and Avakyan, Leon A. and Volochaev, Vadim A. and Mikheykin, Alexey S. and Bdoyan, Karina E. and Zizak, Ivo and Guterman, Vladimir E. and Bugaev, Lusegen A.},
  title = {Effect of Thermal Treatment on the Atomic Structure and Electrochemical Characteristics of Bimetallic PtCu Core–Shell Nanoparticles in PtCu/C Electrocatalysts},
  journal = {J. Phys. Chem. C},
  year = {2018},
  volume = {122},
  number = {30},
  pages = {17199-17210},
  url = {https://doi.org/10.1021/acs.jpcc.8b03696},
  doi = {http://doi.org/10.1021/acs.jpcc.8b03696}
}
Heinz, M., Srabionyan, V.V., Avakyan, L.A., Bugaev, A.L., Skidanenko, A.V., Kaptelinin, S.Y., Ihlemann, J., Meinertz, J., Patzig, C., Dubiel, M. and Bugaev, L.A. Formation of bimetallic gold-silver nanoparticles in glass by UV laser irradiation 2018 J. Alloys Compd.
Vol. 767, pp. 1253-1263 
article DOI URL 
Abstract: Experimental technique for preparing of space arranged arrays of bimetallic AuAg nanoparticles in the near-surface region of glass, exhibiting surface plasmon resonance (SPR) characteristics varying in the wider ranges comparing to monometallic Au, Ag particles or corresponding thin films, is presented together with the structural characterization of the obtained particles. The suggested technique is based on the UV laser irradiation (λ = 193 nm) of the glass surface preliminary doped with silver ions and then sputter coated by a thin gold layer. Optical extinction spectra of the prepared AuAg/glass samples demonstrated strong dependence of SPR upon the number of laser pulses applied. The relationship “SPR characteristics – particles structure and composition – synthesis conditions” was studied using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray fluorescence (XRF) method and X-ray absorption fine structure (XAFS) spectroscopy. The latter provided the structural information on AuAg bonds, which directly evidenced on the formation of bimetallic AuAg nanoparticles in AuAg/glass samples. The XAFS derived values of structural parameters of AuAu and AuAg bonds allowed to visualize the distribution of gold and silver over the volume of representative AuAg nanoparticle and to suggest the most plausible cluster models of the architecture of such particle for the prepared AuAg/glass samples. It was revealed that the core-shell architecture of Au@Ag particles (Au-core, Ag-shell) is the most plausible in AuAg/glass samples prepared by the low number of laser pulses, while the structure of disordered solid solution is suitable for AuAg particles in samples prepared by ∼ 50 and more pulses. Calculations of contributions into experimental optical extinction spectra of AuAg/glass samples from particles with the revealed composition, size and architecture were performed to prove that the proposed structural models of nanoparticles are not in contradiction with the observed optical properties of the samples.
BibTeX:
@article{Srab2018,
  author = {Maximilian Heinz and Vasiliy V. Srabionyan and Leon A. Avakyan and Aram L. Bugaev and Anna V. Skidanenko and Sviatoslav Yu Kaptelinin and Jürgen Ihlemann and Jörg Meinertz and Christian Patzig and Manfred Dubiel and Lusegen A. Bugaev},
  title = {Formation of bimetallic gold-silver nanoparticles in glass by UV laser irradiation},
  journal = {J. Alloys Compd.},
  year = {2018},
  volume = {767},
  pages = {1253-1263},
  url = {http://www.sciencedirect.com/science/article/pii/S0925838818326847},
  doi = {http://doi.org/10.1016/j.jallcom.2018.07.183}
}
Avakyan, L., Heinz, M., Skidanenko, A., Yablunovskiy, K.A., Ihlemann, J., Meinertz, J., Patzig, C., Dubiel, M. and Bugaev, L. Insight on agglomerates of gold nanoparticles in glass based on surface plasmon resonance spectrum: Study by multi-spheres T‑matrix method 2017 J. Phys.: Condens. Matter
Vol. 30(4), pp. 045901-045909 
article DOI URL 
Abstract: Abstract Formation of localized surface plasmon resonance (SPR) spectrum of the randomly distributed gold nanoparticles in the surface layer of silicate float glass, generated and implanted by UV ArF-excimer laser irradiation of thin gold layer sputter coated on the glass surface, was studied by the T-matrix method, which enables taking into account particles agglomerates. The used experimental technique is promising to produce submicron patterns of plasmonic nanoparticles (given by laser masks or gratings) without damaging of the glass surface. Analysis of the applicability of multi-spheres T-matrix (MSTM) method to the studied material was performed through calculations of SPR characteristics for differently arranged and structured gold nanoparticles (gold nanoparticles in solution, particles pairs, core-shell silver-gold nanoparticles) for which either experimental data or results of the modeling by other methods are available. For the studied gold nanoparticles in glass it was revealed that theoretical description of their SPR spectrum requires the consideration of plasmon coupling between particles, which can be effectively done by MSTM calculations. The obtained statistical distributions over particle sizes and over interparticle distances demonstrated the saturation behavior with respect to the number of particles under consideration, which enabled to determine the effective particles aggregate, sufficient to form the SPR spectrum. The suggested technique for the fitting of experimental SPR spectrum of gold nanoparticles in glass by varying the geometrical parameters of particles aggregate in the recurring calculations of spectrum by MSTM method enabled to determine statistical characteristics of the aggregate: the average distance between particles, average size and size distribution of these particles. Presented fitting strategy of SPR spectrum can be applied for nanoparticles of any nature in various substances, and, in principle, can be extended for particles with non-spherical shapes, like ellipsoids, rod-like and other T-matrix-solvable shapes.
BibTeX:
@article{Avakyan2017,
  author = {Leon Avakyan and Maximilian Heinz and Anna Skidanenko and Kirill A. Yablunovskiy and Jürgen Ihlemann and Jörg Meinertz and Christian Patzig and Manfred Dubiel and Lusegen Bugaev},
  title = {Insight on agglomerates of gold nanoparticles in glass based on surface plasmon resonance spectrum: Study by multi-spheres T‑matrix method},
  journal = {J. Phys.: Condens. Matter},
  year = {2017},
  volume = {30},
  number = {4},
  pages = {045901-045909},
  url = {http://iopscience.iop.org/article/10.1088/1361-648X/aa9fcc},
  doi = {http://doi.org/10.1088/1361-648X/aa9fcc}
}
Bulat, N., Avakyan, L., Pryadchenko, V., Srabionyan, V., Belenov, S. and Bugaev, L. Study of carbon-supported bimetallic PtCu nanoparticles by ASAXS 2017 J. Phys: Conf. Ser.
Vol. 848(1), pp. 012027 
article DOI URL 
Abstract: Bimetallic platinum-copper nanoparticles on carbon support are studied as a perspective electrochemical catalyst by anomalous small-angle X-ray scattering near the Pt absorption L 3 -edge. The simultaneous fitting of several diffraction patterns measured at different photon energies lead to a satisfactory agreement between experimental and model curves in the assumption of core-shell structure of the particles with Pt-rich shell and Cu-rich core. It is shown that the average size of as prepared nanoparticles is about 6 nm with distribution spread of about ±2 nm and with thickness of Pt-rich shell approximately 1.6 nm. After annealing at 350o C the average size of the particles increased by two times with additional enlargement of the Pt-rich shell thickness.
BibTeX:
@article{Bulat2017,
  author = {N.V. Bulat and L.A Avakyan and V.V. Pryadchenko and V.V. Srabionyan and S.V. Belenov and L.A. Bugaev},
  title = {Study of carbon-supported bimetallic PtCu nanoparticles by ASAXS},
  journal = {J. Phys: Conf. Ser.},
  year = {2017},
  volume = {848},
  number = {1},
  pages = {012027},
  url = {http://stacks.iop.org/1742-6596/848/i=1/a=012027},
  doi = {http://doi.org/10.1088/1742-6596/848/1/012027}
}
Kolpacheva, N.A., Avramenko, M.V., Avakyan, L.A., Zubavichus, Y.V., Mirzakhanyan, A.A., Manukyan, A.S., Sharoyan, E.G. and Bugaev, L.A. Formation of nickel magnetic nanoparticles and modification of nickel phthalocyanine matrix by sodium doping 2017 Tech. Phys.
Vol. 62(10), pp. 1538-1544 
article DOI URL 
Abstract: Data for the vapor-phase doping (300textdegreeC) of nickel phthalocyanine (NiPc) by sodium taken in different concentrations (x), as well as structural analysis data for Nax=0.2NiPc, Nax=1NiPc, and Nax=3NiPc samples, have been reported. The structure of the samples and their atomic configuration versus the doping level have been studied by transmission electron microscopy, Raman scattering, X-ray diffraction, X-ray absorption spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The structural parameters of Ni--N, Ni--C, and Ni--Ni bonds have been determined, and it has been found that, at a low level of doping by sodium, local structural distortions are observed in some molecules of the NiPc matrix near nickel atoms. The fraction of these molecules grows as the doping level rises from x = 0.2 to x = 1.0. It has been shown that doping changes the oscillation mode of light atoms, which indicates a rise in the electron concentration on five- and six-membered rings. At a high level of sodium doping (x = 3.0), nickel nanoparticles with a mean size of 20 nm and molecule decomposition products have been observed in the NiPc matrix. It has been found that the fraction of nickel atoms in the Nax=3NiPc nanoparticles as estimated from EXAFS data is sufficient for the room-temperature magnetic properties of the samples to persist for a long time.
BibTeX:
@article{Kolpacheva2017,
  author = {Kolpacheva, N. A. and Avramenko, M. V. and Avakyan, L. A. and Zubavichus, Ya. V. and Mirzakhanyan, A. A. and Manukyan, A. S. and Sharoyan, E. G. and Bugaev, L. A.},
  title = {Formation of nickel magnetic nanoparticles and modification of nickel phthalocyanine matrix by sodium doping},
  journal = {Tech. Phys.},
  year = {2017},
  volume = {62},
  number = {10},
  pages = {1538-1544},
  url = {http://dx.doi.org/10.1134/S1063784217100152},
  doi = {http://doi.org/10.1134/S1063784217100152}
}
Pryadchenko, V., Belenov, S., Shemet, D., Volochaev, V., Srabionyan, V., Avakyan, L., Tabachkova, N.Y., Guterman, V. and Bugaev, L. The effect of thermal treatment on the atomic structure of core--shell PtCu nanoparticles in PtCu/C electrocatalysts 2017 Phys. Solid State
Vol. 59(8), pp. 1666-1673 
article DOI URL 
Abstract: PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu2+ and Pt(IV) in a carbon suspension prepared based on an aqueous ethylene glycol solution. The atomic structure of as-prepared PtCu nanoparticles and nanoparticles subjected to thermal treatment at 350°C was examined using PtL3 and CuK EXAFS spectra, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). The results of joint analysis of TEM microphotographs, XRD profiles, and EXAFS spectra suggest that the synthesized electrocatalysts contain PtCu nanoparticles with a Cu core–Pt shell structure and copper oxides Cu2O and CuO. Thermal treatment of electrocatalysts at 350°C results in partial reduction of copper oxides and fusion of bimetallic nanoparticles with the formation of both homogeneous and ordered PtCu solid solutions.

Original Russian Text © V.V. Pryadchenko, S.V. Belenov, D.B. Shemet, V.A. Volochaev, V.V. Srabionyan, L.A. Avakyan, N.Yu. Tabachkova, V.E. Guterman, L.A. Bugaev, 2017, published in Fizika Tverdogo Tela, 2017, Vol. 59, No. 8, pp. 1642–1649.

BibTeX:
@article{Pryadchenko2017,
  author = {Pryadchenko, VV and Belenov, SV and Shemet, DB and Volochaev, VA and Srabionyan, VV and Avakyan, LA and Tabachkova, N Yu and Guterman, VE and Bugaev, LA},
  title = {The effect of thermal treatment on the atomic structure of core--shell PtCu nanoparticles in PtCu/C electrocatalysts},
  journal = {Phys. Solid State},
  year = {2017},
  volume = {59},
  number = {8},
  pages = {1666--1673},
  url = {http://link.springer.com/article/10.1134/S1063783417080200},
  doi = {http://doi.org/10.1134/S1063783417080200}
}
Shemet, D.B., Pryadchenko, V.V., Srabionyan, V.V., Belenov, S.B., Mikheykin, A.S., Avakyan, L.A., Guterman, V.E. and Bugaev, L.A. The effect of thermal treatment on the atomic structure of PtCu core-shell nanoparticles in PtCu/C electrocatalysts 2017 J. Phys: Conf. Ser.
Vol. 848(1), pp. 012018 
article DOI URL 
Abstract: Nanocatalysts PtCu/C with core-shell structure of PtCu nanoparticles were synthesized by the method of sequential chemical reduction of Cu 2+ and Pt(IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of atomic structure of “as prepared” PtCu nanoparticles and obtained after thermal treatment at 350 °C was performed by Pt L 3 - and Cu K -edge extended X-ray absorption fine structure (EXAFS), complemented with TEM and XRD studies. The processing of EXAFS was performed by the technique that enables to reduce the effect of correlations among fitting parameters on the determined values of local structure parameters of the absorbing atoms, which have the nearest surrounding consisting both Pt and Cu atoms.
BibTeX:
@article{Shemet2017,
  author = {D B Shemet and V V Pryadchenko and V V Srabionyan and S B Belenov and A S Mikheykin and L A Avakyan and V E Guterman and L A Bugaev},
  title = {The effect of thermal treatment on the atomic structure of PtCu core-shell nanoparticles in PtCu/C electrocatalysts},
  journal = {J. Phys: Conf. Ser.},
  year = {2017},
  volume = {848},
  number = {1},
  pages = {012018},
  url = {http://stacks.iop.org/1742-6596/848/i=1/a=012018},
  doi = {http://doi.org/10.1088/1742-6596/848/1/012018}
}
Avakyan, L.A., Kolpacheva, N.A., Paramonova, E.V., Singh, J., Hartfelder, U., van Bokhoven, J.A. and Bugaev, L.A. Evolution of the Atomic Structure of Ceria-Supported Platinum Nanocatalysts: Formation of Single Layer Platinum Oxide and Pt-O-Ce and Pt-Ce Linkages 2016 J. Phys. Chem. C
Vol. 120(49), pp. 28057-28066 
article DOI URL 
Abstract: Depending on platinum loading and gas environment vastly different platinum structures in Pt/ceria were observed by Pt L3-edge extended X-ray absorption (EXAFS) and X-ray absorption near-edge (XANES) spectroscopies. Calcination of highly loaded platinum (4 wt %) yielded stacked layers of α-PtO2. The low platinum-loaded sample (2 wt %), obtained by leaching, consisted of a single layer of α-PtO2 bonded to the support by Pt–O–Ce linkages. Reduction of the platinum oxide by exposure to a carbon monoxide and hydrogen (PROX) gas mixture led to complete metal reduction at temperatures above 540 K. Under these conditions platinum–cerium bonds with a distance of 2.4 Å were detected and particles of 0.8 and 0.6 nm for the high-loaded and low-loaded Pt/ceria samples, respectively.
BibTeX:
@article{Avakyan2016,
  author = {Avakyan, Leon A. and Kolpacheva, Natalia A. and Paramonova, Ekaterina V. and Singh, Jagdeep and Hartfelder, Urs and van Bokhoven, Jeroen A. and Bugaev, Lusegen A.},
  title = {Evolution of the Atomic Structure of Ceria-Supported Platinum Nanocatalysts: Formation of Single Layer Platinum Oxide and Pt-O-Ce and Pt-Ce Linkages},
  journal = {J. Phys. Chem. C},
  year = {2016},
  volume = {120},
  number = {49},
  pages = {28057-28066},
  url = {http://dx.doi.org/10.1021/acs.jpcc.6b09824},
  doi = {http://doi.org/10.1021/acs.jpcc.6b09824}
}
Avakyan, L.A., Bulat, N.V., Yablunovski, K.A. and Bugaev, L.A. Amplitudes and Phases of Electron Scattering in Polyatomic Systems for the Structural Analysis of Disordered, Amorphous, and Nanosized Materials via EXAFS Spectroscopy 2016 Bulletin of the Russian Academy of Sciences: Physics
Vol. 80(11), pp. 1347-1349 
article DOI URL 
Abstract: The results from developing and testing a software package for calculating the amplitudes and phases of electron scattering in polyatomic systems are presented. The potential with which an excited electron moves in a medium is constructed using the muffin-tin approximation with Hartree--Fock exchange interaction. Tests of the package for metals, oxides, and iron-bearing water sulphate solutions show that structural parameters can be derived with high degrees of accuracy (the error for interatomic distances is textasciitilde0.01 Å; for coordination numbers, it is textasciitilde7%). Using the developed approach and software, analysis of the Ag K-EXAFS spectra of silver nanoparticles in silica glass allow us to determine the average structural parameters of Ag--O and Ag--Ag bonds.
BibTeX:
@article{Avakyan2016_Izv,
  author = {L. A. Avakyan and N. V. Bulat and K. A. Yablunovski and L. A. Bugaev},
  title = {Amplitudes and Phases of Electron Scattering in Polyatomic Systems for the Structural Analysis of Disordered, Amorphous, and Nanosized Materials via EXAFS Spectroscopy},
  journal = {Bulletin of the Russian Academy of Sciences: Physics},
  year = {2016},
  volume = {80},
  number = {11},
  pages = {1347-1349},
  url = {http://dx.doi.org/10.3103/S1062873816110125},
  doi = {http://doi.org/10.3103/S1062873816110125}
}
Avakyan, L.A., Srabionyan, V.V., Pryadchenko, V.V., Bulat, N.V. and Bugaev, L.A. Construction of Three-Dimensional Models of Bimetallic Nanoparticles Based on X-Ray Absorption Spectroscopy Data 2016 Opt. Spectrosc.
Vol. 120(6), pp. 926-932 
article DOI  
Abstract: A new method for constructing three-dimensional models of bimetallic nanoparticles is proposed.
This method, which is based on X-ray absorption spectroscopy data on the number and type of nearest neigh-
bors, provides information on the distribution of types of atoms over the nanoparticle volume. Its application
to the analysis of the structures of platinum–copper and platinum–silver nanoparticles in the composition of
metal–carbon electrocatalysts has made it possible to distinguish nanoparticles with a core–shell structure
from nanoparticles with a structure of disordered or clustered solid solution.
BibTeX:
@article{Avakyan2016OiS,
  author = {L. A. Avakyan and V. V. Srabionyan and V. V. Pryadchenko and N. V. Bulat and L. A. Bugaev},
  title = {Construction of Three-Dimensional Models of Bimetallic Nanoparticles Based on X-Ray Absorption Spectroscopy Data},
  journal = {Opt. Spectrosc.},
  year = {2016},
  volume = {120},
  number = {6},
  pages = {926-932},
  doi = {http://doi.org/10.1134/S0030400X16060035}
}
Bugaev, L.A., Srabionyan, V.V., Pryadchenko, V.V., Bugaev, A.L., Avakyan, L.A., Belenov, S.V. and Guterman, V.E. Atomic structure of PtCu nanoparticles in PtCu/C catalysts prepared by simultaneous and sequential deposition of components on carbon support 2016 J. Phys: Conf. Ser.
Vol. 712(1), pp. 012048 
article DOI URL 
Abstract: Nanocatalysts PtCu/C with different distribution of components in bimetallic PtCu nanoparticles (NPs) were synthesized by simultaneous and sequential deposition of Cu and Pt on carbon support. Electrochemical stability of the obtained samples PtCu/C was studied using the cyclic voltammetry. Characterization of atomic structure of as prepared PtCu NPs and obtained after acid treatment was performed by Pt L 3 - and Cu K -edge EXAFS using the technique for determining local structure parameters of the absorbing atom under strong correlations among them. EXAFS derived parameters were used for generation of structural models of PtCu NPs by the method of cluster simulations. Within this approach, the models of atomic structure of PtCu NPs obtained by the two methods of synthesis, before and after post treatment and after two months from their preparation were revealed.
BibTeX:
@article{Bugaev2016,
  author = {L A Bugaev and V V Srabionyan and V V Pryadchenko and A L Bugaev and L A Avakyan and S V Belenov and V E Guterman},
  title = {Atomic structure of PtCu nanoparticles in PtCu/C catalysts prepared by simultaneous and sequential deposition of components on carbon support},
  journal = {J. Phys: Conf. Ser.},
  year = {2016},
  volume = {712},
  number = {1},
  pages = {012048},
  url = {http://stacks.iop.org/1742-6596/712/i=1/a=012048},
  doi = {http://doi.org/10.1088/1742-6596/712/1/012048}
}
Bugaev, A.L., Guda, A.A., Lazzarini, A., Lomachenko, K.A., Groppo, E., Pellegrini, R., Piovano, A., Emerich, H., Soldatov, A.V., Bugaev, L.A., Dmitriev, V.P., van Bokhoven, J.A. and Lamberti, C. In situ formation of hydrides and carbides in palladium catalyst: When XANES\ is better than EXAFS\ and XRD\ 2016 Catal. Today
Vol. 283, pp. 119-126 
article DOI URL 
Abstract: Abstract In a number of hydrogenation reactions, palladium nanoparticles may undergo a transition to the hydride or the carbide phase, which affects the catalytic properties. In the current work, we determine the structural evolution of an industrial Pd/C catalyst in the presence of hydrogen and acetylene by means of in situ X-ray absorption spectroscopy and X-ray powder diffraction. We observe reversible hydride phase formation and irreversible formation of the carbide phase. The near-edge structure of the absorption spectra (XANES) plays the key role in distinguishing between hydride and carbide phases. We show that the presence of hydrogen and carbon atoms have a direct effect on the near-edge region which is reproduced by theoretical simulations performed in the Monte-Carlo approach.
BibTeX:
@article{Bugaev2016a,
  author = {Aram L. Bugaev and Alexander A. Guda and Andrea Lazzarini and Kirill A. Lomachenko and Elena Groppo and Riccardo Pellegrini and Andrea Piovano and Hermann Emerich and Alexander V. Soldatov and Lusegen A. Bugaev and Vladimir P. Dmitriev and Jeroen A. van Bokhoven and Carlo Lamberti},
  title = {In situ formation of hydrides and carbides in palladium catalyst: When XANES\ is better than EXAFS\ and XRD\},
  journal = {Catal. Today},
  year = {2016},
  volume = {283},
  pages = {119-126},
  url = {http://www.sciencedirect.com/science/article/pii/S0920586116302255},
  doi = {http://doi.org/10.1016/j.cattod.2016.02.065}
}
Dubiel, M., Heinz, M., Srabionyan, V.V., Pryadchenko, V.V., Avakyan, L.A., Zubavichus, Y.V., Meinertz, J., Ihlemann, J. and Bugaev, L.A. Silver Nanoparticles In Silicate Glass Prepared By Uv Laser Irradiation: Dependences Of Size And Atomic Structure Of Particles Upon Irradiation Parameters 2016 J. Phys: Conf. Ser.
Vol. 712(1), pp. 012110 
article DOI URL 
Abstract: Plasmonic Ag nanostructures were generated in glass surfaces by means of UV laser irradiation (193 nm). The aim of the work was to identify the correlations between the atomic structure of such nanoparticles and their optical properties. The structural characterization of the samples, prepared with different number of laser pulses was performed by Ag K -edge EXAFS. The processing of the spectra by the Fourier-transform analysis gave the values of Ag-Ag and Ag-O interactions averaged over ionic and neutral states of silver in the sample. The consistent analysis of the behavior of features in optical spectra and the obtained dependencies of Ag-Ag and Ag-O structural parameters upon the number of laser pulses enabled to suggest the mechanism of plasmonic Ag nanoparticles formation in silicate glass, which is influenced by the interaction with polyvalent ions (for example Fe 2+ ) and by defect centers (for example HTC and NBOHC centers) generated by UV irradiation.
BibTeX:
@article{Dubiel2016,
  author = {M Dubiel and M Heinz and V V Srabionyan and V V Pryadchenko and L A Avakyan and Ya V Zubavichus and J Meinertz and J Ihlemann and L A Bugaev},
  title = {Silver Nanoparticles In Silicate Glass Prepared By Uv Laser Irradiation: Dependences Of Size And Atomic Structure Of Particles Upon Irradiation Parameters},
  journal = {J. Phys: Conf. Ser.},
  year = {2016},
  volume = {712},
  number = {1},
  pages = {012110},
  url = {http://stacks.iop.org/1742-6596/712/i=1/a=012110},
  doi = {http://doi.org/10.1088/1742-6596/712/1/012110}
}
Heinz, M., Srabionyan, V.V., Bugaev, A.L., Pryadchenko, V.V., Ishenko, E.V., Avakyan, L.A., Zubavichus, Y.V., Ihlemann, J., Meinertz, J., Pippel, E., Dubiel, M. and Bugaev, L.A. Formation of silver nanoparticles in silicate glass using excimer laser radiation: Structural characterization by HRTEM, XRD, EXAFS and optical absorption spectra 2016 J. Alloys Compd.
Vol. 681, pp. 307-315 
article DOI URL 
Abstract: Abstract Plasmonic silver nanostructures in surfaces of soda-lime silicate glasses were generated using Ag+ ↔ Na+ ion exchange and UV\ laser irradiation (ArF laser, 193 nm) with different number of ns laser pulses (from 2 to 5000). To identify the correlations between the optical properties (surface plasmon resonance (SPR) parameters) and atomic structure of silver nanoparticles and their agglomerations, characterization of the samples was performed by HRTEM, XRD, optical absorption in visible range and Ag K-edge EXAFS\ spectra. Analysis of the optical spectra was performed using a Mie theory approach, accounting for the most plausible defect centers in silicate glass like hole trap centers and non-bridging oxygen hole centers. Processing of Ag K-edge EXAFS\ yielded values of Ag-Ag and Ag-O interactions averaged over ionic and neutral states of silver. The consistent treatment of HRTEM\ and XRD\ data, the behavior of features in optical spectra and the obtained dependence of Ag-Ag and Ag-O structural parameters upon the number of laser pulses enabled to suggest a mechanism of plasmonic Ag nanoparticles formation in silicate glass under UV\ laser irradiation.
BibTeX:
@article{Heinz2016,
  author = {Maximilian Heinz and Vasiliy V. Srabionyan and Aram L. Bugaev and Vasiliy V. Pryadchenko and Egor V. Ishenko and Leon A. Avakyan and Yan V. Zubavichus and Jürgen Ihlemann and Jörg Meinertz and Eckhard Pippel and Manfred Dubiel and Lusegen A. Bugaev},
  title = {Formation of silver nanoparticles in silicate glass using excimer laser radiation: Structural characterization by HRTEM, XRD, EXAFS and optical absorption spectra},
  journal = {J. Alloys Compd.},
  year = {2016},
  volume = {681},
  pages = {307-315},
  url = {http://www.sciencedirect.com/science/article/pii/S0925838816311926},
  doi = {http://doi.org/10.1016/j.jallcom.2016.04.214}
}
Kolpacheva, N.A., Avakyan, L.A., Manukyan, A.S., Mirzakhanyan, A.A., Sharoyan, E.G., Pryadchenko, V.V., Zubavichus, Y.V., Trigub, A.L., Fedorenko, A.G. and Bugaev, L.A. Synthesis and Investigation of the Structure of Nanocomposites Based on Nickel Nanoparticles Dispersed in a Phthalocyanine Matrix 2016 Phys. Solid State
Vol. 58(5), pp. 1004-1010 
article DOI  
Abstract: A method based on doping of pure nickel phthalocyanine (NiPc) with a polycrystalline potassium
powder at relatively low temperatures (300°C) has been proposed for the synthesis of a magnetic nanocom-
posite containing nickel nanoparticles stabilized in the NiPc matrix. The structural analysis of the synthesized
nanoparticles and changes in the NiPc initial matrix has been performed using X-ray diffraction, X-ray
absorption spectroscopy, and transmission electron microscopy. It has been found that, at the doping level
used in this study, the synthesized samples of the KxNiPc nanocomposites contain from 9 to 18% Ni in the
form of metallic magnetic nanoparticles with an average size of more than 40 nm. It has been shown that the
formation of nanoparticles is accompanied by a relative misorientation of persistent NiPc molecules with the
unchanged structure of each of these molecules. The stabilization of nickel nanoparticles by the phthalocya-
nine matrix leads to the fact that the synthesized nanocomposites acquire time-conserving magnetic proper-
ties.
BibTeX:
@article{Kolpacheva2016,
  author = {N. A. Kolpacheva and L. A. Avakyan and A. S. Manukyan and A. A. Mirzakhanyan and E. G. Sharoyan and V. V. Pryadchenko and Ya. V. Zubavichus and A. L. Trigub and A. G. Fedorenko and L. A. Bugaev},
  title = {Synthesis and Investigation of the Structure of Nanocomposites Based on Nickel Nanoparticles Dispersed in a Phthalocyanine Matrix},
  journal = {Phys. Solid State},
  year = {2016},
  volume = {58},
  number = {5},
  pages = {1004-1010},
  doi = {http://doi.org/10.1134/S1063783416050103}
}
Pryadchenko, V.V., Srabionyan, V.V., Kurzin, A.A., Bulat, N.V., Shemet, D.B., Avakyan, L.A., Belenov, S.V., Volochaev, V.A., Zizak, I., Guterman, V.E. and Bugaev, L.A. Bimetallic PtCu Core-Shell Nanoparticles in PtCu/C Electrocatalysts: Structural and Electrochemical Characterization 2016 Appl. Catal., A
Vol. 525, pp. 226-236 
article DOI URL 
Abstract: Abstract Composite metal-carbon electrocatalysts PtCu/C containing core-shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu (II) and Pt (IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of “as prepared” and obtained after the acid treatment PtCu nanoparticles was performed by TEM, XRD, Pt L3- and Cu K-edge extended X-ray absorption fine structures (EXAFS). The technique and computational code were proposed for visualization of components distribution over the volume of cluster, which represents the mean bimetallic nanoparticle, according to the values of structural parameters derived from EXAFS. By this technique, the cluster models of PtCu nanoparticles before and after acid treatment, reflecting the character of components’ distribution, were generated. The study of electrochemical performances of the obtained PtCu/C electrocatalyst revealed the similar oxygen reduction reaction (ORR) activity and increased durability compared to commercial Pt/C electrocatalyst E-TEK 20.
BibTeX:
@article{Pryadchenko2016,
  author = {Vasiliy V. Pryadchenko and Vasiliy V. Srabionyan and Alexander A. Kurzin and Natalia V. Bulat and Darya B. Shemet and Leon A. Avakyan and Sergey V. Belenov and Vadim A. Volochaev and Ivo Zizak and Vladimir E. Guterman and Lusegen A. Bugaev},
  title = {Bimetallic PtCu Core-Shell Nanoparticles in PtCu/C Electrocatalysts: Structural and Electrochemical Characterization},
  journal = {Appl. Catal., A},
  year = {2016},
  volume = {525},
  pages = {226-236},
  url = {http://www.sciencedirect.com/science/article/pii/S0926860X1630415X},
  doi = {http://doi.org/10.1016/j.apcata.2016.08.008}
}
Srabionyan, V.V., Pryadchenko, V.V., Kurzin, A.A., Belenov, S.V., Avakyan, L.A., Guterman, V.E. and Bugaev, L.A. Atomic structure of PtCu nanoparticles in PtCu/C catalysts from EXAFS spectroscopy data 2016 Phys. Solid State
Vol. 58(4), pp. 752-762 
article DOI URL 
Abstract: Deposited electrocatalysts with different distributions of components in PtCu bimetallic nanoparticles involved in their composition were synthesized by simultaneous and sequential reduction of Cu(2+) and Pt(IV) in a carbon suspension. The dependence of the atomic structure of PtCu nanoparticles on the synthesis conditions and the degree of influence of post-treatment was established from analysis of the changes in Fourier transforms of the experimental Pt and Cu EXAFS spectra, as well as the structural parameters obtained by their fitting before and after the treatment of the materials in an acid solution. A technique was proposed for visualizing the atomic structure of synthesized bimetallic nanoparticles. This technique made it possible to determine the character of the distribution of the components over the nanoparticle volume in accordance with the component composition and local atomic structure parameters determined from EXAFS spectroscopy and to obtain the visualization of the distribution of the components in PtCu nanoparticles synthesized by the aforementioned methods.
BibTeX:
@article{Srabionyan2016,
  author = {Srabionyan, V. V. and Pryadchenko, V. V. and Kurzin, A. A. and Belenov, S. V. and Avakyan, L. A. and Guterman, V. E. and Bugaev, L. A.},
  title = {Atomic structure of PtCu nanoparticles in PtCu/C catalysts from EXAFS spectroscopy data},
  journal = {Phys. Solid State},
  year = {2016},
  volume = {58},
  number = {4},
  pages = {752-762},
  url = {http://dx.doi.org/10.1134/S1063783416040247},
  doi = {http://doi.org/10.1134/S1063783416040247}
}
Pryadchenko, V.V., Srabionyan, V.V., Mikheykina, E.B., Avakyan, L.A., Murzin, V.Y., Zubavichus, Y.V., Zizak, I., Guterman, V.E. and Bugaev, L.A. Atomic Structure of Bimetallic Nanoparticles in PtAg/C Catalysts: Determination of Components Distribution in the Range from Disordered Alloys to “Core-Shell” Structures 2015 J. Phys. Chem. C
Vol. 119(6), pp. 3217-3227 
article DOI URL 
Abstract: Nanocatalysts PtAg/C with different distributions of components in bimetallic PtAg nanoparticles were synthesized by the methods of simultaneous and sequential reduction of Ag+ and Pt(IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of atomic structure of as prepared PtAg nanoparticles and PtAg nanoparticles obtained after acid treatment at 90 °C was performed by Pt L3-edge extended X-ray absorption fine structure (EXAFS) using the technique for determining local structure parameters of the absorbing Pt atoms, which have the nearest surrounding consisting of Pt and Ag atoms. This technique enabled stable and unambiguous values of parameters for the local structure of Pt atoms in PtAg nanoparticles to be obtained under severe correlations between some of these parameters. The effects of averaging over the sizes and compositions of PtAg nanoparticles on the obtained values of structural parameters were studied by the method of cluster simulations. Analysis of changes in the values of parameters of Pt local structure determined from experimental EXAFS in differently prepared nanoparticles PtAg under acid treatment, supplemented with simulations of different particle architectures by the molecular dynamics (MD) method, enabled a set of evidence of the core–shell structure in these nanoparticles to be proposed. Application of the combined approach, based on the use of EXAFS data and MD simulations, enabled us to characterize the atomic structure of PtAg nanoparticles synthesized by the two methods used and to suggest the mechanism of formation of a platinum shell in nanoparticles obtained by sequential deposition of Pt and Ag atoms on the carbon support, followed by acid treatment.
BibTeX:
@article{Pryadchenko2015,
  author = {Pryadchenko, Vasiliy V. and Srabionyan, Vasiliy V. and Mikheykina, Elena B. and Avakyan, Leon A. and Murzin, Vadim Y. and Zubavichus, Yan V. and Zizak, Ivo and Guterman, Vladimir E. and Bugaev, Lusegen A.},
  title = {Atomic Structure of Bimetallic Nanoparticles in PtAg/C Catalysts: Determination of Components Distribution in the Range from Disordered Alloys to “Core-Shell” Structures},
  journal = {J. Phys. Chem. C},
  year = {2015},
  volume = {119},
  number = {6},
  pages = {3217-3227},
  url = {http://dx.doi.org/10.1021/jp512248y},
  doi = {http://doi.org/10.1021/jp512248y}
}
Bugaev, A.L., Guda, A.A., Lomachenko, K.A., Srabionyan, V.V., Bugaev, L.A., Soldatov, A.V., Lamberti, C., Dmitriev, V.P. and van Bokhoven, J.A. Temperature- and Pressure-Dependent Hydrogen Concentration in Supported PdHx Nanoparticles by Pd K-Edge X-ray Absorption Spectroscopy 2014 J. Phys. Chem. C
Vol. 118(19), pp. 10416-10423 
article DOI URL 
Abstract: Hydride formation in palladium nanoparticles was studied by Pd K-edge X-ray absorption spectroscopy in both the near-edge (XANES) and the extended (EXAFS) regions and by X-ray diffraction (XRD) both in situ as a function of temperature and hydrogen pressure. In contrast to EXAFS and XRD, which probe Pd–Pd interatomic distance changes, the direct effect of hydrogen concentration on the electronic palladium structure is observed in the intensities and the peak positions in the XANES region. By using theoretical simulations, we propose a simple analysis of hydrogen concentration based on the changes of relative peak amplitudes in the XANES region, which correlate with interatomic distance changes determined by both EXAFS and XRD. By the quantitative analysis of XANES difference spectra, we have developed a scheme to determine the hydrogen concentration in palladium nanoparticles without applying any additional calibration procedures with alternative experimental techniques.
BibTeX:
@article{Bugaev2014,
  author = {Aram L. Bugaev and Alexander A. Guda and Kirill A. Lomachenko and Vasiliy V. Srabionyan and Lusegen A. Bugaev and Alexander V. Soldatov and Carlo Lamberti and Vladimir P. Dmitriev and Jeroen A. van Bokhoven},
  title = {Temperature- and Pressure-Dependent Hydrogen Concentration in Supported PdHx Nanoparticles by Pd K-Edge X-ray Absorption Spectroscopy},
  journal = {J. Phys. Chem. C},
  year = {2014},
  volume = {118},
  number = {19},
  pages = {10416-10423},
  url = { 
http://dx.doi.org/10.1021/jp500734p

}, doi = {http://doi.org/10.1021/jp500734p} }
Pryadchenko, V., Galustov, A., Srabionyan, V. and Bugaev, L. Determination of the local atomic structure of material from X-ray absorption spectroscopy data without fourier analysis of experimental spectra 2014 Opt. Spectrosc.
Vol. 117(2), pp. 187-193 
article DOI URL 
Abstract: A technique for analyzing the extended X-ray absorption fine structure spectra of an atom in different structural states in a material under study is proposed. This technique makes it possible to determine the parameters of the nearest environment of absorbing atoms without applying Fourier filtering and related techniques. The proposed approach is tested by an example of the L3 absorption spectra of platinum, obtained by direct calculation for models of one-component platinum nanoparticles and bimetallic Pt-Ag nanoparticles with different core and shell structures. The error in determining the structural parameters is analyzed, and the range of applicability of the technique proposed is discussed.
BibTeX:
@article{Pryadchenko2014,
  author = {Pryadchenko, V.V. and Galustov, A.D. and Srabionyan, V.V. and Bugaev, L.A.},
  title = {Determination of the local atomic structure of material from X-ray absorption spectroscopy data without fourier analysis of experimental spectra},
  journal = {Opt. Spectrosc.},
  publisher = {Pleiades Publishing},
  year = {2014},
  volume = {117},
  number = {2},
  pages = {187-193},
  url = {http://dx.doi.org/10.1134/S0030400X14080207},
  doi = {http://doi.org/10.1134/S0030400X14080207}
}
Srabionyan, V.V., Bugaev, A.L., Pryadchenko, V.V., Avakyan, L.A., van Bokhoven, J.A. and Bugaev, L.A. EXAFS Study of Size Dependence of Atomic Structure in Palladium Nanoparticles 2014 J. Phys. Chem. Solids
Vol. 75(4), pp. 470-476 
article DOI URL 
Abstract: Dependence of atomic structure of Palladium nanoparticles on supports Al2O3 and SiO2 upon their size, changed from 1.3 to 10.5 nm, was studied by Pd K-edge EXAFS. To determine the structure of the interior (core) and the near surface regions of nanoparticle, the fitting technique of the Fourier-transforms F(R) of spectra was used, which enabled to overcome instabilities of the obtained structural parameters values. The processing of experimental data was performed using results of the study of features formation in │F(R)│ of Pd K-EXAFS in Pd foil. By this approach it was revealed that the local structure of Pd atoms in the core is similar to fcc structure of bulk Pd, irrespective of size. The percentage of Pd atoms, which can be attributed to the core, upon the particles size was determined and the obtained dependence was described by the “cluster size equation”. In the near surface region of nanoparticles, nearest-neighbors Pd–Pd distances show a large Debye–Waller parameters and the mean bond length slightly contracted for nanoparticles of sizes less than  2 nm. The effect of small structural distortions in the vicinity of absorbing Pd atom in the near surface region was studied using the cluster model of nanoparticle.
BibTeX:
@article{Srabionyan2014,
  author = {Vasiliy V. Srabionyan and Aram L. Bugaev and Vasiliy V. Pryadchenko and Leon A. Avakyan and Jeroen A. van Bokhoven and Lusegen A. Bugaev},
  title = {EXAFS Study of Size Dependence of Atomic Structure in Palladium Nanoparticles},
  journal = {J. Phys. Chem. Solids},
  year = {2014},
  volume = {75},
  number = {4},
  pages = {470-476},
  url = {http://www.sciencedirect.com/science/article/pii/S0022369713003971},
  doi = {http://doi.org/10.1016/j.jpcs.2013.12.012}
}
Avakyan, L., Manukyan, A., Mirzakhanyan, A., Sharoyan, E., Zubavichus, Y., Trigub, A., Kolpacheva, N. and Bugaev, L. Atomic Structure of Nickel Phthalocyanine Probed by X-Ray Absorption Spectroscopy and Density Functional Simulations 2013 Opt. Spectrosc.
Vol. 114(3), pp. 347-352 
article URL 
BibTeX:
@article{Avakyan2013,
  author = {Avakyan, LA and Manukyan, AS and Mirzakhanyan, AA and Sharoyan, EG and Zubavichus, YV and Trigub, AL and Kolpacheva, NA and Bugaev, LA},
  title = {Atomic Structure of Nickel Phthalocyanine Probed by X-Ray Absorption Spectroscopy and Density Functional Simulations},
  journal = {Opt. Spectrosc.},
  publisher = {Springer},
  year = {2013},
  volume = {114},
  number = {3},
  pages = {347-352},
  url = {http://link.springer.com/article/10.1134/S0030400X1303003X}
}
Srabionyan, V.V., Bugaev, A.L., Pryadchenko, V.V., Makhiboroda, A.V., Rusakova, E.B., Avakyan, L.A., Schneider, R., Dubiel, M. and Bugaev, L.A. EXAFS study of changes in atomic structure of silver nanoparticles in soda-lime glass caused by annealing 2013 J. Non-Cryst. Solids
Vol. 382, pp. 24-31 
article DOI URL 
Abstract: Atomic structure of silver nanoparticles in soda-lime glass at T = 10 K before and after annealing was studied by Ag K-edge EXAFS. To overcome ambiguities in the structure determination by the Fourier-transform analysis of these spectra, caused by the presence of various species of the absorbing silver atoms in the sample, the refinements of the fitting technique of the Fourier transforms F(R) have been implemented. The F(R) of Ag K-edge EXAFS\ in as prepared and annealed glasses were analyzed in the extended range of interatomic distances (R) up to  6.5 A using Ag K-edge EXAFS\ in Ag-foil at the same temperature as the reference. The proposed technique of the fit enabled to go beyond the averaged description of silver nanoparticles structure in glass and to reveal the atomic structure of the core region of nanoparticles, the structural characteristics of their near-surface region, parameters of AgO bonds inside the glass matrix and the percentage of Ag atoms in each of these species before and after the annealing process. The mean size of silver nanoparticles in as prepared and annealed glasses was estimated and the mechanism of nanoparticles growth after the thermal treatment was suggested.
BibTeX:
@article{Srabionyan2013,
  author = {Vasiliy V. Srabionyan and Aram L. Bugaev and Vasiliy V. Pryadchenko and Alexander V. Makhiboroda and Elizaveta B. Rusakova and Leon A. Avakyan and Reinhard Schneider and Manfred Dubiel and Lusegen A. Bugaev},
  title = {EXAFS study of changes in atomic structure of silver nanoparticles in soda-lime glass caused by annealing},
  journal = {J. Non-Cryst. Solids},
  year = {2013},
  volume = {382},
  pages = {24-31},
  url = {http://www.sciencedirect.com/science/article/pii/S002230931300505X},
  doi = {http://doi.org/10.1016/j.jnoncrysol.2013.09.025}
}
Manukyan, A., Mirzakhanyan, A., Badalyan, G., Shirinyan, G., Fedorenko, A., Lianguzov, N., Yuzyuk, Y., Bugaev, L. and Sharoyan, E. Nickel nanoparticles in carbon structures prepared by solid-phase pyrolysis of nickel-phthalocyanine 2012 J. Nanopart. Res.
Vol. 14, pp. 1-7 
article DOI URL 
BibTeX:
@article{Manukyan2012,
  author = {Manukyan, A.S. and Mirzakhanyan, A.A. and Badalyan, G.R. and Shirinyan, G.H. and Fedorenko, A.G. and Lianguzov, N.V. and Yuzyuk, Yu.I. and Bugaev, L.A. and Sharoyan, E.G.},
  title = {Nickel nanoparticles in carbon structures prepared by solid-phase pyrolysis of nickel-phthalocyanine},
  journal = {J. Nanopart. Res.},
  publisher = {Springer Netherlands},
  year = {2012},
  volume = {14},
  pages = {1-7},
  url = {http://link.springer.com/article/10.1007%2Fs11051-012-0982-6},
  doi = {http://doi.org/10.1007/s11051-012-0982-6}
}
Manukyan, A.S., Mirzakhanyan, A.A., Khachatryan, T.K., Badalyan, G.R., Abdulvakhidov, K.G., Bugaev, L.A. and Sharoyan, E.G. Copper-carbon nanocomposites prepared by sold-phase pyrolysis of copper phthalocyanine 2012 J. Contemp. Physics (Armenian Ac. Sci.)
Vol. 47(6), pp. 292-295 
article DOI URL 
Abstract: By using solid-phase pyrolysis of copper phthalocyanine we have prepared copper nanoparticles in carbon matrices. The elemental composition, structure, and morphology of nanocomposites were investigated by scanning electron microscopy, energy dispersive X-ray microanalysis, and X-ray diffraction. Depending on the temperature and time of pyrolysis, the sizes of copper nanoparticles can be varied from 10 nm to 400 nm. The structure of carbon matrices also strongly depends on the pyrolysis conditions, which allows us to synthesize nanocomposites with given properties.
BibTeX:
@article{Manukyan2012a,
  author = {Manukyan, A. S. and Mirzakhanyan, A. A. and Khachatryan, T. K. and Badalyan, G. R. and Abdulvakhidov, K. G. and Bugaev, L. A. and Sharoyan, E. G.},
  title = {Copper-carbon nanocomposites prepared by sold-phase pyrolysis of copper phthalocyanine},
  journal = {J. Contemp. Physics (Armenian Ac. Sci.)},
  year = {2012},
  volume = {47},
  number = {6},
  pages = {292--295},
  url = {https://doi.org/10.3103/S1068337212060084},
  doi = {http://doi.org/10.3103/S1068337212060084}
}
Pryadchenko, V.V., Srabionyan, V.V., Avakyan, L.A., van Bokhoven, J.A. and Bugaev, L.A. Electronic Structure of Pt and Au Compounds Measured by X-ray Emission and X-ray Absorption Spectroscopies 2012 J. Phys. Chem. C
Vol. 116(49), pp. 25790-25796 
article DOI URL 
Abstract: The electronic structure of the filled and unfilled states and the formation of the chemical bonding in PtO2, PtCl4, PtS2, and Au2S are studied by measured Pt and Au Lβ5 X-ray emission spectra (XES) and L3-edge X-ray absorption spectra (XAS). The study is based on the comparative analysis of the calculated local partial densities of electronic states (LPDOS) on the noble atom and on the neighboring ligands. It is revealed that theoretical description of experimental spectra requires going beyond MT-approximation and therefore the full-potential linearized augmented-plane-wave method realized in the code WIEN2k is applied. The effect of a static screened 2p core-hole potential of Pt and Au on the calculated Pt L3-edge XAS is examined with a supercell approach. The obtained agreement of theoretical spectra with the experimental ones validates the results of the LPDOS analysis and the made conclusions on electronic structure of the studied compounds.
BibTeX:
@article{Pryadchenko2012,
  author = {Pryadchenko, Vasiliy V. and Srabionyan, Vasiliy V. and Avakyan, Leon A. and van Bokhoven, Jeroen A. and Bugaev, Lusegen A.},
  title = {Electronic Structure of Pt and Au Compounds Measured by X-ray Emission and X-ray Absorption Spectroscopies},
  journal = {J. Phys. Chem. C},
  year = {2012},
  volume = {116},
  number = {49},
  pages = {25790-25796},
  url = {http://pubs.acs.org/doi/abs/10.1021/jp3073409},
  doi = {http://doi.org/10.1021/jp3073409}
}
Bugaev, L.A., Avakyan, L.A., Srabionyan, V.V. and Bugaev, A.L. Resolution of Interatomic Distances in the Study of Local Atomic Structure Distortions by Energy-restricted X-Ray Absorption Spectra 2010 Phys. Rev. B
Vol. 82, pp. 064204 
article DOI URL 
Abstract: Applicability of the existing criteria for signal frequencies resolution to the problem of close interatomic distances determination by energy-restricted x-ray absorption spectra is studied within the approach based on the Fourier transformation and fitting procedures. Without losing generality, theoretical signals χ(k) of different k dependencies are used and among them—the signals χ(k) of x-ray absorption spectroscopy (k is the photoelectron’s wave number). The last ones are calculated at different values of two interatomic distances R1 and R2 in a model of radial distribution of coordinating atoms in relation to the absorbing center, including the values of distances, which can’t be resolved a priori according to the criteria. It is revealed that the boundary value of ΔR=|R2−R1|, at which the model of local structure distortions can be distinguished among other alternative ones by the used approach depends strongly upon the coincidence of the functional form of k dependence used for the fitting function with that of the studied signal χ(k), well known in x-ray absorption spectroscopy. In the case of coincidence, the boundary value of ΔR obtained by the restricted intervals Δk∼3 or 4 Å−1 is approximately ten times smaller than that predicted by the existing criteria. The effect of statistical noise in spectrum intensity on the established ΔR value is analyzed.
BibTeX:
@article{Bugaev2010,
  author = {Bugaev, L. A. and Avakyan, L. A. and Srabionyan, V. V. and Bugaev, A. L.},
  title = {Resolution of Interatomic Distances in the Study of Local Atomic Structure Distortions by Energy-restricted X-Ray Absorption Spectra},
  journal = {Phys. Rev. B},
  publisher = {American Physical Society},
  year = {2010},
  volume = {82},
  pages = {064204},
  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.82.064204},
  doi = {http://doi.org/10.1103/PhysRevB.82.064204}
}
Manukyan, A.S., Mirzakhanyan, A.A., Butaeva, T.I., Guda, A.A., Soldatov, A.V., Bugaev, L.A., Asatryan, H.R., Baranov, P.G. and Sharoyan, E.G. Room-temperature molecular ferromagnetism based on nickel phthalocyanine. Magnetic resonance, optical and xanes spectra 2010 Armenian J. of Phys
Vol. 3(3), pp. 272-275 
article  
Abstract: A method of synthesis of room-temperature ferromagnetic samples of nickel phthalocyanine (NiPc) doped with K and Rb atoms has been developed. These materials are air-stable and have a Curie temperature higher than 300oC. Measurements of optical spectra show that the doping leads to the essential changes in spectra, in particular, to the shift of peaks in the visible range. In the spectra of magnetic resonance of doped samples an intense wide asymmetric line of ferromagnetic resonance and a narrow signal with g ≈ 2 is observed. In order to reveal the nature of ferromagnetism of the obtained compounds and to determine the nearest local environment of Ni ions, the spectra of X- ray absorption near-edge structure (XANES) were also measured.
BibTeX:
@article{Manukyan2010,
  author = {Manukyan, A. S. and Mirzakhanyan, A. A. and Butaeva, T. I. and Guda, A. A. and Soldatov, A. V. and Bugaev, L. A. and Asatryan, H. R. and Baranov, P. G. and Sharoyan, E. G.},
  title = {Room-temperature molecular ferromagnetism based on nickel phthalocyanine. Magnetic resonance, optical and xanes spectra},
  journal = {Armenian J. of Phys},
  year = {2010},
  volume = {3},
  number = {3},
  pages = {272-275}
}
Bugaev, L.A., van Bokhoven, J.A., Khrapko, V.V., Avakyan, L.A. and Latokha, V.J. Effect of Aluminum on the Local Structure of Silicon in Zeolites as Studied by Si K Edge X-ray Absorption Near-Edge Fine Structure: Spectra Simulation with a Non-Muffin Tin Atomic Background 2009 J. Phys. Chem. B
Vol. 113(14), pp. 4614-4618 
article DOI URL 
Abstract: Experimental Si K edge X-ray absorption near-edge fine structure (XANES) of zeolite faujasite, mordenite, and beta are interpreted by means of the FEFF8 code, replacing the theoretical atomic background μ0 by a background that was extracted from an experimental spectrum. To some extent, this diminished the effect of the inaccuracy introduced by the MT potential and accounted for the intrinsic loss of photoelectrons. The agreement of the theoretical and experimental spectra at energies above the white lines enabled us to identify structural distortion around silicon, which occurs with increasing aluminum content. The Si K edge XANES spectra are very sensitive to slight distortions in the silicon coordination. Placing an aluminum atom on a nearest neighboring T site causes a distortion in the silicon tetrahedron, shortening one of the silicon−oxygen bonds relative to the other three.
BibTeX:
@article{Bug2009,
  author = {Bugaev, Lusegen A. and van Bokhoven, Jeroen A. and Khrapko, Valerii V. and Avakyan, Leon A. and Latokha, V. Jana},
  title = {Effect of Aluminum on the Local Structure of Silicon in Zeolites as Studied by Si K Edge X-ray Absorption Near-Edge Fine Structure: Spectra Simulation with a Non-Muffin Tin Atomic Background},
  journal = {J. Phys. Chem. B},
  year = {2009},
  volume = {113},
  number = {14},
  pages = {4614-4618},
  url = {http://pubs.acs.org/doi/abs/10.1021/jp8098285},
  doi = {http://doi.org/10.1021/jp8098285}
}
Bugaev, L.A., Avakyan, L.A., Makhova, M.S., Dmitrienko, E.V. and Alekseenko, I.B. Resolution of Interatomic Distances by Fourier Analysis of Short Energy-Range X-Ray Absorption Spectra 2008 Opt. Spectrosc.
Vol. 105, pp. 881 
article DOI URL 
Abstract: Based on the example of signals with a known form of functional dependence, as is the case in
Xframe0ray absorption spectroscopy (XAS), the applicability of the available general estimates of the frequency res-
olution limits in the case of determining two close interatomic distances by a Fourier analysis of short energy
range XAS spectra is considered. A method for the Fourier analysis of such spectra over a small interval of pho-
toelectron wavenumbers,  3frame14 Åframe21, is proposed. The method is applied to the K-XAS spectra of As calculated
for different pressure-induced distortions of the nearest environment of the As atom in an InAs crystal. This
made it possible to identify an adequate model for the radial distribution of coordinating In atoms among alter-
native models and, based on this model, to resolve two As–In distances that differ by 0.03 Å. A Fourier analysis
of the experimental As K-XAS spectrum of an InAs crystal subjected to a pressure of 11 GPa performed based
on this method made it possible to determine the character of distortions of the nearest environment of the As
atom under this pressure; namely, it was found that the radial distribution of the six coordinating In atoms cor-
responds to the (1 + 4 + 1) model. For this distortion model, the As–In interatomic distances were determined.
BibTeX:
@article{Bugaev2008,
  author = {L. A. Bugaev and L. A. Avakyan and M. S. Makhova and E. V. Dmitrienko and I. B. Alekseenko},
  title = {Resolution of Interatomic Distances by Fourier Analysis of Short Energy-Range X-Ray Absorption Spectra},
  journal = {Opt. Spectrosc.},
  year = {2008},
  volume = {105},
  pages = {881},
  url = {http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=optics&number=12&year=8&page=881},
  doi = {http://doi.org/10.1134/S0030400X08120114}
}
Bugaev, L.A., Latokha, Y.V., Avakyan, L.A., Aquilanti, G. and Pascarelli, S. XAFS Study of Local Atomic Structure in InAs at Low Pressures 2007 AIP Conf. Proc.
Vol. 882(1), pp. 395-397 
article DOI URL 
BibTeX:
@article{Bug2007,
  author = {L. A. Bugaev and Y. V. Latokha and L. A. Avakyan and G. Aquilanti and S. Pascarelli},
  title = {XAFS Study of Local Atomic Structure in InAs at Low Pressures},
  journal = {AIP Conf. Proc.},
  publisher = {AIP},
  year = {2007},
  volume = {882},
  number = {1},
  pages = {395-397},
  url = {http://link.aip.org/link/?APC/882/395/1},
  doi = {http://doi.org/10.1063/1.2644536}
}
Bugaev, L.A., van Bokhoven, J.A., Avakyan, L.A. and Latokha, Y.V. Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites 2007 AIP Conf. Proc.
Vol. 882(1), pp. 117-119 
article DOI URL 
BibTeX:
@article{Bug2007csat,
  author = {L. A. Bugaev and J. A. van Bokhoven and L. A. Avakyan and Ya. V. Latokha},
  title = {Non-MT Determination of X-Ray Absorption Cross-Section's Factorized Atomic Part in the Near-Edge Region. Application to Si K-Edge XANES Analysis in Beta-Zeolites},
  journal = {AIP Conf. Proc.},
  publisher = {AIP},
  year = {2007},
  volume = {882},
  number = {1},
  pages = {117-119},
  url = {http://link.aip.org/link/?APC/882/117/1},
  doi = {http://doi.org/10.1063/1.2644446}
}
Bugaev, L.A., Latokha, Y.V., Avakyan, L.A. and Fain, E.Y. Determination of the Factorized Atomic Part of the X-ray Absorption Cross Section in the Near-Edge Spectrum: Application to the Analysis of Structural Changes in Beta-Zeolite with an Increase in the Aluminum Content 2007 Opt. Spectrosc.
Vol. 102(6), pp. 867 
article DOI URL 
Abstract: A technique for determining the factorized atomic part at(k) of the X-ray absorption cross section
in the near-edge range of small photoelectron wave numbers k, based on the selection of this function from the
experimental absorption spectrum of the atom in a compound, has been developed. This technique has been
tested using the X-ray absorption near-edge structure (XANES) spectra of aluminum and silicon in a number
of model compounds with known structure and applied to investigation of changes in the character of the short-
range environment of a silicon atom in zeolite with a variable Si/Al ratio. Use of the function at(k) obtained
by the developed technique in the ab initio calculation of the XANES spectra of silicon in a model zeolite
with Si/Al = 100 makes it possible to reduce the effect of the errors of the muffin-tin approximation on the fine
structure of the calculated spectrum and substantiate the possibility of comparing relative changes in a certain
spectral range with a change in the structure of the short-range environment of silicon in zeolite with an
increase in the aluminum content. On the basis of this approach, the formation of local distortions in the oxygen
tetrahedron coordinating an ionized silicon atom with an increase in the aluminum content (decrease in the
Si/Al ratio from 100 to 12) has been established.
BibTeX:
@article{Bugaev2007,
  author = {L. A. Bugaev and Ya. V. Latokha and L. A. Avakyan and E. Ya. Fain},
  title = {Determination of the Factorized Atomic Part of the X-ray Absorption Cross Section in the Near-Edge Spectrum: Application to the Analysis of Structural Changes in Beta-Zeolite with an Increase in the Aluminum Content},
  journal = {Opt. Spectrosc.},
  year = {2007},
  volume = {102},
  number = {6},
  pages = {867},
  url = {http://www.maik.ru/cgi-perl/search.pl?type=abstract&name=optics&number=6&year=7&page=867},
  doi = {http://doi.org/10.1134/S0030400X07060100}
}
Bugaev, L.A., Latokha, Y.V., Avakyan, L.A. and van Bokhoven, E.A. Determination of Temperature-Induced Changes in the Structure of the Nearest Environment of Aluminum in Mordenite Zeolites from X-ray Absorption Near-Edge Structure Spectra 2006 Opt. Spectrosc.
Vol. 100, pp. 563 
article  
Abstract: The structure of the nearest environment of aluminum in mordenite zeolites was investigated at temperatures up to 1000 K using the Al K x-ray absorption near-edge structure (XANES) spectra. The inter-atomic Al–O distances and the number of coordinating oxygen atoms were determined by Fourier transformation of Al K-XANES spectra and fitting of the contribution of the nearest oxygen atoms. The exactness and stability of the obtained values of structural parameters were verified using the Al K-XANES spectrum of the model Na-mordenite zeolite. To determine the coordination of aluminum in H-mordenites in the temperature range under study, fitting of the contribution of coordinating oxygen atoms was performed using both the single-sphere model of the nearest environment of aluminum and two-sphere fitting for the most probable structural models of the nearest environment of aluminum. Such models were chosen based on the analysis of the specific preedge features and fine structure of the XANES spectra, as well as NMR data. With this approach, the simultaneous presence of tetra- and hexacoordinated aluminum in H-mordenite at T = 300 K was established and the concentrations of such mixed states were determined. The presence of strong distortions of the oxygen tetrahedron coordinating the aluminum atom in dehydrated H-mordenite at 575 K was shown and the Al–O distances for such distortions were determined. The simultaneous presence of tri- and tetracoordinated aluminum in H-mordenite at 985 K was established and the fraction of tricoordinated aluminum was estimated quantitatively.
BibTeX:
@article{Bugaev2006,
  author = {L. A. Bugaev and Ya. V. Latokha and L. A. Avakyan and E. A. van Bokhoven},
  title = {Determination of Temperature-Induced Changes in the Structure of the Nearest Environment of Aluminum in Mordenite Zeolites from X-ray Absorption Near-Edge Structure Spectra},
  journal = {Opt. Spectrosc.},
  year = {2006},
  volume = {100},
  pages = {563}
}
Bugaev, L.A., van Bokhoven, J.A., Sokolenko, A.P., Latokha, Y.V. and Avakyan, L.A. Local Structure of Aluminum in Zeolite Mordenite as Affected by Temperature 2005 J. Phys. Chem. B
Vol. 109(21), pp. 10771-10778 
article DOI URL 
Abstract: The local aluminum structure in zeolite mordenite was studied at temperatures up to 1000 K in a vacuum by Al K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The interatomic aluminum−oxygen distances and the number of coordinating oxygen atoms were determined by Fourier transform analyses of experimental Al K-edge XANES spectra and the fits of the nearest oxygen atoms contributions, using a limited number of variables. The values of fixed parameters for Fourier transform and fit are established from the spectrum of Na−mordenite, considered the reference compound for the studied zeolites H−mordenites, which was also used to test the accuracy and the stability of the determined structural parameters. To reveal the aluminum coordination in H−mordenite at various temperatures, the Fourier transform peak of the coordinating oxygen polyhedron was fitted first with a single-shell model, and the obtained structural information was refined by the fits, on the basis of the most plausible models for the aluminum coordination environment. The choice of such models for each temperature was performed according to the qualitative predictions on the aluminum local atomic structure provided by the preedge data analysis and 27Al magic angle spinning (MAS) NMR experiments. By this method, the presence of sixfold aluminum atoms, aside from the fourfold ones, in H−mordenite at room temperature was revealed quantitatively, and the concentrations of these mixed coordinations were determined; the structural distortion of the oxygen tetrahedron around aluminum in dehydrated H−mordenite at T = 575 K was found to be strong, and the corresponding Al−O distances for this distortion were obtained; for H−mordenite at 985 K, the presence of threefold coordinated aluminum atoms, aside from the fourfold ones, was revealed, and an estimate of the amount of threefold aluminum was given.
BibTeX:
@article{Bug2005Al,
  author = {Bugaev, Lusegen A. and van Bokhoven, Jeroen A. and Sokolenko, Andrei P. and Latokha, Yana V. and Avakyan, Leon A.},
  title = {Local Structure of Aluminum in Zeolite Mordenite as Affected by Temperature},
  journal = {J. Phys. Chem. B},
  year = {2005},
  volume = {109},
  number = {21},
  pages = {10771-10778},
  url = {http://pubs.acs.org/doi/abs/10.1021/jp0508709},
  doi = {http://doi.org/10.1021/jp0508709}
}
Bugaev, L., Farges, F., Rusakova, E., Sokolenko, A., Latokha, Y. and Avakyan, L. Fe coordination environment in Fe(II)- and Fe(III)-silicate glasses via the Fourier-transform analysis of Fe K-XANES 2005 Phys. Scr.
Vol. 115, pp. 215-217 
article DOI URL 
Abstract: The Fe-O distances ( R 1 ) and the number of nearest oxygen atoms ( N 1 ), which coordinate Fe in Fe(II) and Fe(III) containing silicate glasses are determined by the method based on the Fourier-transform analysis of XANES performed for the short k -range and the subsequent fit of the extracted first shell's contribution. The scattering amplitudes for Fe-O pair, used for the fit, are calculated by the HF MT-potential with the neutral electronic configurations of atoms. The validity of this model for the different redox states of Fe in glasses and the accuracy of the determined ( R 1 ) and ( N 1 ) are analyzed applying the method to the Fe K-XANES of the references – Fe(II) and Fe(III) aqueous sulfate solutions. The modeling of the contribution of the Fe nearest oxygens to the Fe KXANES of Fe(II)- and Fe(III)-rich silicate glasses, as well as in the series of glasses with the mixture of Fe(II) and Fe(III) states, performed through a single-shell fit and a subsequent two-shell fit, provides structural parameters for the oxygen-polyhedron around the ionized Fe 2+ and Fe 3+ atoms and gives access to the estimates for the Fe 2+ /Fe 3+ ratio changes among all samples studied.
BibTeX:
@article{Bug2005Fe,
  author = {L Bugaev and F Farges and E Rusakova and A Sokolenko and Ya Latokha and L Avakyan},
  title = {Fe coordination environment in Fe(II)- and Fe(III)-silicate glasses via the Fourier-transform analysis of Fe K-XANES},
  journal = {Phys. Scr.},
  year = {2005},
  volume = {115},
  pages = {215-217},
  url = {http://stacks.iop.org/1402-4896/2005/i=T115/a=054},
  doi = {http://doi.org/10.1238/Physica.Topical.115a00215}
}
Bugaev, L., Farges, F., Rusakova, E., Sokolenko, A., Latokha, Y. and Avakyan, L. The Fourier-transform analysis of Ti K-XANES in metamicts and glasses 2005 Phys. Scr.
Vol. 115(T115), pp. 168 
article DOI URL 
Abstract: The structural parameters of Ti coordination environment in glassy titanite (CaTiSiO 5 ), natisite (Na 2 TiSiO 5 ) and radiation damaged CaTiSiO 5 are determined by the method proposed earlier, based on the Fourier-transform analysis of Ti K-XANES over the short k -range of photoelectrons wave numbers. The accuracy of the determined parameters is tested for the model crystals CaTiSiO 5 , Na 2 TiSiO 5 . The modelling of the extracted contribution into Ti-XANES, arising from the oxygen-polyhedron around the ionised Ti atom in amorphous titanites and natisite, performed via the single-shell fit and the two-shells fit, returns not only the averaged structural parameters, but also reveals the main groups of the Ti–O distances for this polyhedron.
BibTeX:
@article{Bug2005Ti,
  author = {L Bugaev and F Farges and E Rusakova and A Sokolenko and Ya Latokha and L Avakyan},
  title = {The Fourier-transform analysis of Ti K-XANES in metamicts and glasses},
  journal = {Phys. Scr.},
  year = {2005},
  volume = {115},
  number = {T115},
  pages = {168},
  url = {http://stacks.iop.org/1402-4896/2005/i=T115/a=039},
  doi = {http://doi.org/10.1238/Physica.Topical.115a00168}
}
Bugaev, L.A., Sokolenko, A.P., Dmitrienko, H.V., Grishkan, V.Y. and Flank, A.-M. Determination of distances and coordination numbers in amorphous compounds by XANES. Application to diopside glas 2002 Phys.Chem.Glasses
Vol. 43C, pp. 35-37 
article  
BibTeX:
@article{Bugaev2002,
  author = {Bugaev, L. A. and Sokolenko,A. P. and Dmitrienko, H. V. and Grishkan, V. Yu. and Flank, A.-M.},
  title = {Determination of distances and coordination numbers in amorphous compounds by XANES. Application to diopside glas},
  journal = {Phys.Chem.Glasses},
  year = {2002},
  volume = {43C},
  pages = {35-37}
}
Bugaev, L.A., Shuvaeva, V.A., Zhuchkov, K.N., Rusakova, E.B. and Vedrinskii, R.V. The temperature dependence for the third shell's Fourier-peak of Nb-EXAFS in KNbO3 as additional source of information on the local atomic structure 2001 J. Sync. Rad.
Vol. 8, pp. 308-310 
article  
Abstract: The information on the structure of tetragonal KNbO3 is extracted from the temperature dependence of the third shell's Fourier-peak of Nb-EXAFS. It is shown that this dependence can be explained by two effects: 1) rigid rotations of the O6-octahedron and 2) increase of the third shell's DW-parameter. However, diffraction data on the temperature dependence of the DW-parameter permit us to conclude that the last effect only is sufficient and the O6-octahedron rotation doesn't occur in the high-temperature phases of KNbO3. Using EXAFS it is revealed that in the neighboring cells Nb-atoms are parallel shifted closely to 211 direction in tetragonal phase.
BibTeX:
@article{Bug2001,
  author = {L A Bugaev and V A Shuvaeva and K N Zhuchkov and E B Rusakova and R V Vedrinskii},
  title = {The temperature dependence for the third shell's Fourier-peak of Nb-EXAFS in KNbO3 as additional source of information on the local atomic structure},
  journal = {J. Sync. Rad.},
  year = {2001},
  volume = {8},
  pages = {308-310}
}
Bugaev, L.A., Sokolenko, A.P., Dmitrienko, H.V. and Flank, A.-M. Fourier Filtration of XANES As a Source of Quantitative Information of Interatomic Distances and Coordination Numbers in Crystalline Minerals and Amorphous Compounds 2001 Phys. Rev. B
Vol. 65, pp. 024105 
article DOI URL 
Abstract: The method for quantitative determination of interatomic distances and coordination numbers (CN) in minerals and amorphous compounds by their x-ray absorption near edge structure (XANES) is proposed. The generation of the method and the proof of its main points are based on the revealed theoretical description of XANES for crystalline compounds and minerals as a sum of different photoelectron scattering processes on two- and approximately linear three-atoms chains, originated at the absorbing atom. The method consists of the Fourier filtration (FF) of the experimental XANES within the short range of photoelectron’s wave numbers and the following fitting, with three varied parameters, of the first shell term extracted by the FF procedure. The accuracy of the obtained local structural parameters is illustrated for the reference crystalline minerals, which are used also to simulate the XANES formation in glasses. The application of the method to Mg XANES in diopside-glass and its crystalline equivalent, Diopside, permits one to determine the Mg-O distance and CN for the first oxygen shell around the Mg atom and to reveal the change of these parameters between the glass and the crystal with similar chemical composition.
BibTeX:
@article{Bugaev2001,
  author = {Bugaev, L. A. and Sokolenko, A. P. and Dmitrienko, H. V. and Flank, A.-M.},
  title = {Fourier Filtration of XANES As a Source of Quantitative Information of Interatomic Distances and Coordination Numbers in Crystalline Minerals and Amorphous Compounds},
  journal = {Phys. Rev. B},
  publisher = {American Physical Society},
  year = {2001},
  volume = {65},
  pages = {024105},
  url = {http://link.aps.org/doi/10.1103/PhysRevB.65.024105},
  doi = {http://doi.org/10.1103/PhysRevB.65.024105}
}
Bugaev, L.A., Ildefonse, P., Flank, A.M., Sokolenko, A.P. and Dmitrienko, H.V. Determination of interatomic distances and coordination numbers by K-XANES in crystalline minerals with distorted local structure 2000 J. Phys.: Condens. Matter
Vol. 12(6), pp. 1119 
article DOI URL 
Abstract: The method for quantitative determination of interatomic distances and coordination numbers (CN) from experimental K-XANES of light metallic atoms in crystalline compounds with distorted local structure is proposed, based on the extraction of the first shell term and the multiple-scattering term. In crystalline minerals the extraction of these terms can be obtained under uncertainties of  0.3 - 0.4 Å in the values of the second and more distant shell radii, using the unambiguous diffraction data on cell unit parameters and the type of point symmetry. The fitting of the extracted first shell term by theoretical terms, generated within alternative models for the split of this shell under the local structure distortions in the environment of the absorbing metallic atom, permits one to obtain the interatomic distances and CN in reasonable quantitative agreement with the diffraction data for the reference compounds studied.
BibTeX:
@article{Bugaev2000,
  author = {L A Bugaev and Ph Ildefonse and A M Flank and A P Sokolenko and H V Dmitrienko},
  title = {Determination of interatomic distances and coordination numbers by K-XANES in crystalline minerals with distorted local structure},
  journal = {J. Phys.: Condens. Matter},
  year = {2000},
  volume = {12},
  number = {6},
  pages = {1119},
  url = {http://stacks.iop.org/0953-8984/12/i=6/a=328},
  doi = {http://doi.org/10.1088/0953-8984/12/6/328}
}
Bugaev, L., Shuvaeva, V., Alekseenko, I., Zhuchkov, K. and Vedrinskii, R. Determination of the local structure of NbO6 octahedra in the orthorhombic phase of a KNbO3 crystal using EXAFS 1998 Phys. Solid State
Vol. 40, pp. 1001-1005 
article URL 
Abstract: A new method proposed by us to determine the displacement direction of B atoms from centrosymmetric positions in ABO 3 crystals is used to study the local atomic structure of KNbO 3 in the orthorhombic phase. It is shown that the conventional treatment of the EXAFS yields serious errors in determinations of the local distortions of NbO 6 octahedrons. To eliminate these errors, it is suggested that diffraction data on the average atomic displacements should be combined with the results of direct calculations of the Nb K -EXAFS of KNbO 3 in the orthorhombic phase. This approach was used to establish that the preferential direction of displacement of Nb in the orthorhombic phase of KNbO 3 is in the direction of the polar twofold axis.
BibTeX:
@article{Bugaev1998,
  author = {Bugaev, L. and Shuvaeva, V. and Alekseenko, I. and Zhuchkov, K. and Vedrinskii, R.},
  title = {Determination of the local structure of NbO6 octahedra in the orthorhombic phase of a KNbO3 crystal using EXAFS},
  journal = {Phys. Solid State},
  publisher = {MAIK Nauka/Interperiodica distributed exclusively by Springer Science+Business Media LLC.},
  year = {1998},
  volume = {40},
  pages = {1001-1005},
  note = {10.1134/1.1130466},
  url = {http://dx.doi.org/10.1134/1.1130466}
}
Bugaev, L.A., Ildefonse, P., Flank, A.M., Sokolenko, A.P. and Dmitrienko, H.V. Aluminum K-XANES spectra in minerals as a source of information on their local atomic structure 1998 J. Phys.: Condens. Matter
Vol. 10, pp. 5463-5473 
article  
Abstract: For Al containing compounds with different symmetry types of Al environment (from fourfold to 12-fold coordinated Al) it is revealed that Al K-XANES spectra are well reproduced by the XAFS code, based on the method of Hartree-Fock MT-potential generation, considering the photoelectron single-, double- and triple-scattering processes on approximately linear two- and three-atom chains, originated at the absorbing Al atom. The empirical 'selection rules' for choosing these chains are obtained and the origins of features in spectra are interpreted using the SELCOMP code. The proposed EXAFS-like approach for AI K-XANES description is applied also to explain the differences in Al K-XANES spectra, caused by the replacement of Fe atoms by Al atoms in goethite (alpha-FeOOH).
BibTeX:
@article{Bugaev1998a,
  author = {L A Bugaev and P Ildefonse and A M Flank and A P Sokolenko and H V Dmitrienko},
  title = {Aluminum K-XANES spectra in minerals as a source of information on their local atomic structure},
  journal = {J. Phys.: Condens. Matter},
  year = {1998},
  volume = {10},
  pages = {5463-5473}
}
Bugaev, L.A., Vedrinskii, R.V., Levin, I.G. and Airapetian, V.M. Crystalline potential for photoelectron scattering phase-shift calculations and X-ray absorption spectra of Ti in crystals 1991 J. Phys.: Condens. Matter
Vol. 3(45), pp. 8967 
article URL 
Abstract: X-ray absorption spectra (XAS) of Ti in crystals of Ti metal, TiC, TiN and TiO 2 rutile are calculated in EXAFS and XANES regions. Single, double and triple photoelectron scattering processes are included through the spherical-wave formalism and the crystalline muffin-tin (MT) potential model, which employs a Hartree-Fock exchange interaction between photoelectron and core electrons inside MT spheres. Overall agreement of the theoretical and experimental spectra is obtained on the absolute photon energy scale. This result enables one to treat the experimental XAFS without using adjustable parameter E 0 . The neutral-atoms approximation is shown to be adequate for the phase-shift calculations in XAS theory for both metals and insulators. A comparison of Ti K XAFS of Ti metal calculated by means of various exchange-correlation potentials for the photoelectrons inside MT spheres is carried out. The best results are shown to be provided by Hartree-Fock and Dirac-Hara exchange potentials.
BibTeX:
@article{Bugaev1991,
  author = {L A Bugaev and R V Vedrinskii and I G Levin and V M Airapetian},
  title = {Crystalline potential for photoelectron scattering phase-shift calculations and X-ray absorption spectra of Ti in crystals},
  journal = {J. Phys.: Condens. Matter},
  year = {1991},
  volume = {3},
  number = {45},
  pages = {8967},
  url = {http://stacks.iop.org/0953-8984/3/i=45/a=018}
}
Vedrinskii, R.V., Bugaev, L.A. and Airapetian, V.M. The problem of potential construction and phaseshift calculation in X-ray-absorption spectra theory of molecules and complexes containing low-Z atoms 1991 J. Phys. B: At., Mol. Opt. Phys.
Vol. 24(8), pp. 1967 
article URL 
Abstract: K X-ray absorption spectra of molecules and complexes containing low-Z atoms (CO, CO 2 , OCS, ferrocene) are studied. Agreement of theoretical and experimental spectra on the photon energy scale is obtained if the electron scattering phaseshifts and amplitudes are calculated with the help of the spherical wave formalism and the non-local Hartree-Fock muffin-tin (MT) potential, constructed so as to provide the potential continuity on MT sphere surfaces. In the case of molecules and complexes the approach proposed enables one to determine MT zero position in relation to the absorption threshold without any fitting procedure.
BibTeX:
@article{Vedrinskii1991,
  author = {R V Vedrinskii and L A Bugaev and V M Airapetian},
  title = {The problem of potential construction and phaseshift calculation in X-ray-absorption spectra theory of molecules and complexes containing low-Z atoms},
  journal = {J. Phys. B: At., Mol. Opt. Phys.},
  year = {1991},
  volume = {24},
  number = {8},
  pages = {1967},
  url = {http://stacks.iop.org/0953-4075/24/i=8/a=014}
}
Bugaev, L., Vedrinskii, R. and Levin, I. Spherical wave formalism in the bond-angle determination problem by EXAFS\ 1989 Physica B
Vol. 158(1-3), pp. 378-382 
article DOI URL 
BibTeX:
@article{Bugaev1989,
  author = {L.A. Bugaev and R.V. Vedrinskii and I.G. Levin},
  title = {Spherical wave formalism in the bond-angle determination problem by EXAFS\ },
  journal = {Physica B},
  year = {1989},
  volume = {158},
  number = {1-3},
  pages = {378-382},
  url = {http://www.sciencedirect.com/science/article/pii/0921452689903177},
  doi = {http://doi.org/10.1016/0921-4526(89)90317-7}
}
Bugaev, L.A., Gegusin, I.I., Datsyuk, V.N., Novakovich, A.A. and Vedrinskii, R.V. Multiple scattering approach to the XANES theory of alkali halide crystals. I. Crystalline potential in the X-Ray absorption spectra problem 1986 Physica Status Solidi (B)
Vol. 133(1), pp. 195-202 
article DOI URL 
Abstract: Two schemes of the crystalline potential for the slow electron in the conduction band of alkalihalides are proposed. The first one (semiempirical) is based on the assumption that in the case of an ion in the crystal one can use the same energy dependence of logarithmic derivatives (of radial solutions at the atomic sphere radius) as in the case of the isolated ion. The modifications required consist in some potential corrections, that are due to the Madelung field as well as to the relaxation and polarization response for both, hole and electron. The second model (ab initio) suggests the straightforward solution of Poisson's equation. Both approaches are compared, so it is found that they lead to satisfactory agreement for a wide energy interval in the continuum.
BibTeX:
@article{Bugaev1986,
  author = {Bugaev, L. A. and Gegusin, I. I. and Datsyuk, V. N. and Novakovich, A. A. and Vedrinskii, R. V.},
  title = {Multiple scattering approach to the XANES theory of alkali halide crystals. I. Crystalline potential in the X-Ray absorption spectra problem},
  journal = {Physica Status Solidi (B)},
  publisher = {WILEY-VCH Verlag},
  year = {1986},
  volume = {133},
  number = {1},
  pages = {195-202},
  url = {http://dx.doi.org/10.1002/pssb.2221330123},
  doi = {http://doi.org/10.1002/pssb.2221330123}
}
Vedrinskii, R., Bugaev, L., Gegusin, I., Kraizman, V., Novakovich, A., Prosandeev, S., Ruus, R., Maiste, A. and Elango, M. X-ray absorption near edge structure (XANES) for KCl 1982 Solid State Commun.
Vol. 44(10), pp. 1401-1407 
article DOI URL 
Abstract: The cluster calculations of K and L2,3 edge XANES of K and Cl in KCl within the multiple scattering theory formalism using nonlocal HF potentials with abd without consideration of core hole field were performed. For K spectra the influence of the core hole potential is rather weak and the results are similar to those obtained with Xα potentials. For L2,3 spectra, particularly for that of K+, core hole field leads to a radical redistribution of oscillator strength caused mainly by the spatial rearrangement of d like states. Calculated XANES curves show good over-all agreement with the experimental spectra (the L2,3 absorption of K+ in KCl was measured using the synchrotron radiation of the USSR Academy of Sciences storage ring VEPP-2M in Novosibirsk).
BibTeX:
@article{Vedrinskii1982,
  author = {R.V. Vedrinskii and L.A. Bugaev and I.I. Gegusin and V.L. Kraizman and A.A. Novakovich and S.A. Prosandeev and R.E. Ruus and A.A. Maiste and M.A. Elango},
  title = {X-ray absorption near edge structure (XANES) for KCl},
  journal = {Solid State Commun.},
  year = {1982},
  volume = {44},
  number = {10},
  pages = {1401-1407},
  url = {http://www.sciencedirect.com/science/article/pii/0038109882900199},
  doi = {http://doi.org/10.1016/0038-1098(82)90019-9}
}