JabRef references

Author	Title	Year	Journal/Proceedings	Reftype	DOI/URL
Sukharina, G., Ermakova, A., Alekseev, R., Shakhgildyan, G., Veligzhanin, A., Avakyan, L., Bugaev, L. and Sigaev, V.	Effect of B2O3 concentration on the local atomic structure of lanthanum in lanthanum-borate glasses: XANES study and the principle of crystal-chemical similarity of the short-range order in glasses and crystals [Abstract] [BibTeX]	2023	J. Non-Cryst. Solids accepted	article	DOI
Abstract: .
BibTeX: @article{Sukharina2023, author = {G.B. Sukharina and A.М. Ermakova and R.O. Alekseev and G.Yu. Shakhgildyan and A.A. Veligzhanin and L.A. Avakyan and L.A. Bugaev and V.N. Sigaev}, title = {Effect of B2O3 concentration on the local atomic structure of lanthanum in lanthanum-borate glasses: XANES study and the principle of crystal-chemical similarity of the short-range order in glasses and crystals}, journal = {J. Non-Cryst. Solids}, publisher = {Elsevier BV}, year = {2023}, volume = {accepted for publication (Ref.: Ms No. NOC-D-23-00445)}, pages = {}, doi = {} }
Srabionyan, V., Avakyan, L., Durymanov, V., Rubanik, D., Viklenko, I., Skunova, A. and Bugaev, L.	Atomic structure and optical properties of color centers of silver in AgAu/glass irradiated by UV laser [Abstract] [BibTeX]	2023	J Phys Chem Solids Vol. 79, pp. 111412	article	DOI
Abstract: A study of the structural states of silver in glass after Ag+↔Na+ ion-exchange and further irradiation with different numbers of UV laser pulses has been performed using Ag K-edge XANES combined with DFT simulations and the processing of Ag K-EXAFS. Theoretical Ag K-edge XANES, calculated for DFT-generated structural models, showed high sensitivity to the number of nearest oxygen neighbors of the absorbing Ag+ ion, to changes in the corresponding interatomic distances RAg-O (changes ≳ 0.05 Å) and bond angles (changes ≳ 10° at apical Ag in atomic chain O–Ag–O), and to the presence of Ag+ ions among the second neighbors of Ag. The effect of more distant O and Si neighbors can be considered negligible. The applied combination of complementary techniques for structural analysis of the color centers of silver in glass has revealed that, after ion-exchange, Ag+ ions are predominantly present in glass in the form of dimers, in which the two Ag+ ions are separated by an interatomic distance, RAg-Ag, of 3.4 Å. Other interatomic distances RAg-O in the dimers have also been obtained. It has been determined that, under laser irradiation with the number of pulses up to 1000, only a small proportion (up to 10%) of Ag+ ions in glass samples is reduced from the states of isolated ions and the revealed Ag dimers present after Ag+↔Na+ ion-exchange. The reduced Ag atoms form monometallic Ag NPs and are also deposited on the surface of Au NPs, forming bimetallic AgAu NPs with a solid solution structure. The processes of the formation, growth, and dissolution of monometallic Ag NPs and bimetallic AgAu NPs with increasing number of laser pulses are discussed. Analysis of the blue shifts of ca. 20 nm of localized surface plasmon resonances (LSPRs) of Ag NPs with increasing number of UV laser pulses up to 1000 revealed that these shifts occurred due to a decrease in the average size of optically visible Ag NPs caused by the growth of initially less visible small Ag NPs (≲5 nm) and partial dissolution of the largest particles.
BibTeX: @article{Srabionyan2023, author = {Vasiliy V. {Srabionyan} and Leon A. Avakyan and Veniamin A. Durymanov and Darya S. Rubanik and Ivan A. Viklenko and Anna V. Skunova and Lusegen A. Bugaev}, journal = {Journal of Physics and Chemistry of Solids}, title = {Atomic structure and optical properties of color centers of silver in AgAu/glass irradiated by UV laser}, year = {2023}, pages = {111412}, volume = {179}, doi = {https://doi.org/10.1016/j.jpcs.2023.111412}, }
Alekseev, R., Avakyan, L., Shakhgildyan, G., Komandin, G., Savinkov, V., Romanov, N., Veligzhanin, A., Lebedev, S., Ermakova, A., Sukharina, G., Bugaev, L. and Sigaev, V.	Local atomic structure of the high refractive index La2O3–Nb2O5–B2O3 glasses [Abstract] [BibTeX]	2022	J Alloy Compd Vol. 917, pp. 165357	article	DOI
Abstract: High refractive glasses in the La2O3–Nb2O5–B2O3 (LNB) system were synthesized by the melt-quenching technique and correlations between their compositions and structural features were clarified. It was found that the refraction index of the LNB glasses is tunable from 1.71 to 1.98 by the variation of the Nb2O5 fraction from 5 to 30 mol%. The infrared spectroscopy analysis implies on the presence of three and four coordinated borate units, as well as six coordinated niobium atoms. The X-ray absorption (La L3-edge and Nb K-edge XANES and EXAFS) spectroscopy and total X-ray scattering results show that niobium atoms maintain octahedral oxygen coordination despite the wide variation of the Nb2O5 content, while average lanthanum coordination number is versatile and changes from 8 to 10. The interatomic distance values testify that the niobium octahedra in the glass network are connected only “by corners”. The stability of niobium local atomic structure implies that the main source of the changes in the optical properties of studied glasses is the variation of the Nb2O5 content. The deeper understanding of the local atomic structure of the high refractive index LNB glasses paves ways for the development of new glass wafers for cutting-edge augmented reality devices.
BibTeX: @article{Alekseev2022, author = {R.O. Alekseev and L.A. Avakyan and G.Yu. Shakhgildyan and G.A. Komandin and V.I. Savinkov and N.A. Romanov and A.A. Veligzhanin and S.P. Lebedev and A.M. Ermakova and G.B. Sukharina and L.A. Bugaev and V.N. Sigaev}, title = {Local atomic structure of the high refractive index La2O3–Nb2O5–B2O3 glasses}, journal = {J Alloy Compd}, publisher = {Elsevier BV}, year = {2022}, volume = {917}, pages = {165357}, doi = {https://doi.org/10.1016/j.jallcom.2022.165357} }
Avakyan, L., Tolchina, D., Barkovski, V., Belenov, S., Alekseenko, A., Shaginyan, A., Srabionyan, V., Guterman, V. and Bugaev, L.	Ultimate sensitivity of radial distribution functions to architecture of PtCu bimetallic nanoparticles [Abstract] [BibTeX]	2022	Comput. Mater. Sci. Vol. 208, pp. 111326	article	DOI URL
Abstract: Bimetallic nanoparticles containing platinum and another d-metal are highly perspective catalysts with stability and activity superior to a single-metal platinum materials. It is known that the improvement of catalytic properties depends both from the composition and from the structural arrangement of atoms in bimetallic nanoparticles. This leads to importance of the experimental determination of the nanoparticles architecture (random solid solution, Janus, core–shell or “gradient”) for the search of novel bimetallic systems. We considered the platinum–copper nanoparticles synthesized by simultaneous or multistage sequential depositions of metals. The insight of the architecture of bimetallic PtCu nanoparticles was obtained by the study of radial distribution functions (RDFs) of metal atoms. The RDFs were obtained both theoretically, using molecular dynamics simulations, and experimentally, from the analysis of the extended X-ray absorption fine structure (EXAFS) spectra at Pt L3- and Cu K- edges. Machine learning (ML) algorithms revealed the outstanding sensitivity of the theoretical RDFs to the architecture of the bimetallic nanoparticles: the correct architecture can be determined with 99 % confidence in terms of F1 score. The application of the variety of ML classification methods to the experimental RDFs showed the benefit K-Neighbors classification method.
BibTeX: @article{Avakyan2022, author = {L. Avakyan and D. Tolchina and V. Barkovski and S. Belenov and A. Alekseenko and A. Shaginyan and V. Srabionyan and V. Guterman and L. Bugaev}, title = {Ultimate sensitivity of radial distribution functions to architecture of PtCu bimetallic nanoparticles}, journal = {Comput. Mater. Sci.}, publisher = {Elsevier BV}, year = {2022}, volume = {208}, pages = {111326}, url = {https://www.sciencedirect.com/science/article/pii/S0927025622001148}, doi = {https://doi.org/10.1016/j.commatsci.2022.111326} }
Gyulasaryan, H., Avakyan, L., Emelyanov, A., Sisakyan, N., Kubrin, S., Srabionyan, V., Ovcharov, A., Dannangoda, C., Bugaev, L., Sharoyan, E., Angelakeris, M., Farle, M., Spasova, M., Martirosyan, K. and Manukyan, A.	Iron-cementite nanoparticles in carbon matrix: Synthesis, structure and magnetic properties [Abstract] [BibTeX]	2022	J Magn Magn Mater, pp. 169503	article	DOI
Abstract: Carbon encapsulated iron-cementite Fe–Fe3C nanoparticles with “core–shell” architecture, were synthesized by a single-step solid-state pyrolysis of iron phthalocyanine at the temperature 900 °C with pyrolysis time of 180 min. The morphology and size distribution of the fabricated nanocomposites have been investigated using high resolution transmission and scanning transmission electron microscopies which revealed Fe–Fe3C nanoparticles with an average diameter of about 7.5 nm embedded in a carbon matrix. The structure, composition, and morphology of Fe–FeC nanoparticles in the carbon matrix were analyzed by X-ray based techniques combined with Reactive Force-Field Molecular Dynamics simulations, Mössbauer spectroscopy to outline the “core–shell” architecture. Such evidence is further supported by the magnetic features of hysteresis loops at 10 and 300 K as well as the magnetization of Fe–FeC nanoparticles is properly approximated with magnetic contributions of Fe and FeC bulk counterparts.
BibTeX: @article{Gyulasaryan_2022, author = {H. Gyulasaryan and L. Avakyan and A. Emelyanov and N. Sisakyan and S. Kubrin and V. Srabionyan and A. Ovcharov and C. Dannangoda and L. Bugaev and E. Sharoyan and M. Angelakeris and M. Farle and M. Spasova and K. Martirosyan and A. Manukyan}, title = {Iron-cementite nanoparticles in carbon matrix: Synthesis, structure and magnetic properties}, journal = {J Magn Magn Mater}, publisher = {Elsevier BV}, year = {2022}, pages = {169503}, doi = {https://doi.org/10.1016/j.jmmm.2022.169503} }
Manukyan, A., Gyulasaryan, H., Kocharian, A., Oyala, P., Chumakov, R., Avramenko, M., Sanchez, C., Bernal, O.O., Bugaev, L. and Sharoyan, E.	Structure and Magnetism of Few-Layer Nanographene Clusters in Carbon Microspheres [Abstract] [BibTeX]	2022	J. Phys. Chem. C Vol. 126(1), pp. 493-504	article	DOI
Abstract: The solid-phase pyrolysis method was used to synthesize carbon microspheres, consisting of clusters of few-layer nanographene and amorphous carbon. Powders of metal-free phthalocyanine and polyethylene served as precursors of the synthesized carbon microspheres. The pyrolysis products of metal-free phthalocyanine samples SPc(700) and SPc(900) contained 4 and 1 atom % nitrogen, respectively, replacing carbon in the graphene lattice in pyrrolic and pyridinic coordination. There are no impurity nitrogen atoms in the products of the pyrolysis of polyethylene. The SPc(700) sample showed strong paramagnetism with a concentration of paramagnetic centers of ∼5 × 1019 spin g–1 and a temperature-independent diamagnetism susceptibility of χDia = −1 × 10–6 emu g–1 Oe–1. In a temperature range of 5–300 K, ferromagnetism was also revealed with a temperature dependence similar to that of ferromagnetic cluster spin glasses, with maximum saturation magnetization, MSFM = 3 × 10–2 emu g–1, and coercive force, Hc = 400 Oe, at Tsg = 25 K. It was shown that the ferromagnetism in the SPc(700) sample is due to π(p)-electrons of zigzag-type edge states as well as nitrogen impurity atoms. The experimental results are interpreted based on the temperature dependence of the spin correlation length. It was revealed that the temperature dependence of the integral of the magnetic resonance absorption intensity closely resembles the temperature behavior of the saturation magnetization of the ferromagnetic component.
BibTeX: @article{Manukyan_2022, author = {Aram Manukyan and Harutyun Gyulasaryan and Armen Kocharian and Paul Oyala and Ratibor Chumakov and Marina Avramenko and Carlos Sanchez and Oscar O. Bernal and Lusegen Bugaev and Eduard Sharoyan}, title = {Structure and Magnetism of Few-Layer Nanographene Clusters in Carbon Microspheres}, journal = {J. Phys. Chem. C}, publisher = {American Chemical Society (ACS)}, year = {2022}, volume = {126}, number = {1}, pages = {493--504}, doi = {https://doi.org/10.1021/acs.jpcc.1c06748} }
Shakhgildyan, G., Durymanov, V., Ziyatdinova, M., Atroshchenko, G., Golubev, N., Trifonov, A., Chereuta, O., Avakyan, L., Bugaev, L. and Sigaev, V.	Effect of Gold Nanoparticles on the Crystallization and Optical Properties of Glass in ZnO-MgO-Al2O3-SiO2 System [Abstract] [BibTeX]	2022	Crystals Vol. 12(2), pp. 287	article	DOI
Abstract: Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al2O3-SiO2 glass containing TiO2 and ZrO2 as nucleating agents. X-ray diffraction, transmission electron microscopy, Raman, and optical spectroscopy were used for the study. We showed that gold nanoparticles have no effect on the formation of gahnite nanocrystals during the glass heat treatments, while optical properties of the glass-ceramics are strongly dependent on the gold addition. A computational model was developed to predict optical properties of glass during the crystallization, and the possibility for adjusting the localized surface plasmon resonance band position with the heat treatment temperature was shown.
BibTeX: @article{Shakhgildyan2022, author = {Georgiy Shakhgildyan and Veniamin Durymanov and Mariam Ziyatdinova and Grigoriy Atroshchenko and Nikita Golubev and Alexey Trifonov and Olga Chereuta and Leon Avakyan and Lusegen Bugaev and Vladimir Sigaev}, title = {Effect of Gold Nanoparticles on the Crystallization and Optical Properties of Glass in ZnO-MgO-Al2O3-SiO2 System}, journal = {Crystals}, publisher = {MDPI AG}, year = {2022}, volume = {12}, number = {2}, pages = {287}, doi = {https://doi.org/10.3390/cryst12020287} }
Shakhgildyan, G., Avakyan, L., Ziyatdinova, M., Atroshchenko, G., Presnyakova, N., Vetchinnikov, M., Lipatiev, A., Bugaev, L. and Sigaev, V.	Tuning the plasmon resonance of gold nanoparticles in phase-separated glass via the local refractive index change [Abstract] [BibTeX]	2021	J. Non-Cryst. Solids Vol. 566, pp. 120893	article	DOI URL
Abstract: Gold-doped glasses are of interest for plasmonics and photonics as optical media with well-resolved localized surface plasmon resonance (LSPR). We showed the possibility for the thermally-controlled tuning of the LSPR band position of gold nanoparticles precipitated in the ZnO-MgO-Al2O3-SiO2 glass nucleated by TiO2 and ZrO2 nucleators. The maximal red-shift of the LSPR band as high as 100 nm was achieved for glass which is characterized by the presence of 10 nm phase-separated regions and ≈ 4 nm precipitated gold nanoparticles. The fitting of the absorption spectra showed that the distinct red-shift of the LSPR band is caused by the increased refractive index of the surrounding medium (in the interval 1.6–2.6). The described scenario of the LSPR band shift driven by the phase-separation represents a new approach for precise plasmonic tuning of gold nanoparticles in glass and paves the way for the development of new glass-based materials for photonics applications.
BibTeX: @article{Shakhgildyan2021, author = {G. Shakhgildyan and L. Avakyan and M. Ziyatdinova and G. Atroshchenko and N. Presnyakova and M. Vetchinnikov and A. Lipatiev and L. Bugaev and V. Sigaev}, title = {Tuning the plasmon resonance of gold nanoparticles in phase-separated glass via the local refractive index change}, journal = {J. Non-Cryst. Solids}, publisher = {Elsevier BV}, year = {2021}, volume = {566}, pages = {120893}, url = {http://dx.doi.org/10.1016/j.jnoncrysol.2021.120893}, doi = {https://doi.org/10.1016/j.jnoncrysol.2021.120893} }
Srabionyan, V.V., Sukharina, G.B., Kurzina, T.I., Durymanov, V.A., Ermakova, A.M., Avakyan, L.A., Alayon, E.M.C., Nachtegaal, M., van Bokhoven, J.A. and Bugaev, L.A.	Atomic Structure of Cu Centers in Mordenite Formed by Interaction of Copper Chloride with H-MOR Zeolite and Temperature Treatment [Abstract] [BibTeX]	2021	J. Phys. Chem. C	article	DOI
Abstract: The eﬀect of temperature on the formation of copper centers in Cu- mordenite (Cu-MOR), obtained by solid-state ion exchange between copper chloride and zeolite H-mordenite, was studied by combining Density Functional Theory (DFT) simulations of the local atomic structures of copper with the analysis of Cu K-edge XANES and EXAFS, measured “in situ” from room temperature to 400 °C. Cu K edge XANES and EXAFS spectra have a diﬀerent level of sensitivity regarding the detection of the angular and radial distribution of atoms in the closest vicinity of copper. Based on this, a simultaneous theoretical description of XANES and Fourier transforms F(R) of EXAFS in the extended range of interatomic distances R (up to ∼6 Å) was used as an eﬃcient ﬁlter for selecting suitable atomic models of copper species from the number of models given by DFT. It was revealed that, between RT and ∼200 °C, the local structure around copper in Cu-MOR did not change and was similar to that of bulk CuCl. By increasing the temperature to 300 °C and then to 400 °C, changes in both Cu K-edge XANES and EXAFS were observed, indicating the reconstruction of the local structure of copper. At 300 °C, copper-containing fragments, with a CuCl-like structure, decompose to form two diﬀerent types of copper centers in the vicinity of the eight-member rings of the zeolite framework. The ﬁrst type contains one copper atom, a monomer, coordinated to three O atoms of the framework as ﬁrst neighbors and an O, an Al, and two Si atoms as the next neighbors. The second type contains two Cu atoms, which form a dimer, in which each Cu atom has two O atoms and one Cl atom as the ﬁrst neighbors and one Al and two Si atoms as the next neighbors. At 400 °C, the Cu−Cu interaction in all the structural models, which describe the Cu K-edge XAS spectra, led to the assumption that the formation of dicopper centers dominated. Furthermore, the simultaneous description of both Cu XANES and EXAFS suggested the necessity of doing the structural analysis based on a single dicopper model of the Cu center and to also consider linear combinations of other such models. The suitable linear combination was found based on the three most plausible structural models of the Cu environment containing a Cu−Cl−Cu chain, in which each copper atom is characterized by a very similar pair radial distribution function of the neighboring atoms. However, the angular distributions of these neighboring atoms are diﬀerent in all three Cu centers due to the diﬀerence in the nonequivalent crystallographic sites of the Al atoms, near which the Cu centers formed in the zeolite framework. In Cu-MOR at 400 °C another type of Cu center, containing a Cu−O−Cu dimer, can exist simultaneously with the above-mentioned Cu centers with Cu−Cl−Cu dimers.
BibTeX: @article{Srabionyan2021, author = {Vasiliy V. Srabionyan and Galina B. Sukharina and Tatyana I. Kurzina and Veniamin A. Durymanov and Alexandra M. Ermakova and Leon A. Avakyan and Evalyn Mae C. Alayon and Maarten Nachtegaal and Jeroen A. van Bokhoven and Lusegen A. Bugaev}, title = {Atomic Structure of Cu Centers in Mordenite Formed by Interaction of Copper Chloride with H-MOR Zeolite and Temperature Treatment}, journal = {J. Phys. Chem. C}, publisher = {American Chemical Society (ACS)}, year = {2021}, doi = {https://doi.org/10.1021/acs.jpcc.1c08240} }
Avakyan, L., Manukyan, A., Bogdan, A., Gyulasaryan, H., Coutinho, J., Paramonova, E., Sukharina, G., Srabionyan, V., Sharoyan, E. and Bugaev, L.	Synthesis and structural characterization of iron-cementite nanoparticles encapsulated in carbon matrix [Abstract] [BibTeX]	2020	J. Nanopart. Res. Vol. 22(1)	article	DOI URL
Abstract: Carbon-encapsulated iron-cementite (Fe-Fe3C) nanoparticles, promising nanomaterials for medicine due to their valuable magnetic properties, were synthesized by a single-step solid-state pyrolysis of iron phthalocyanine. To obtain required magnetic characteristics of such nanoparticles by governing of the pyrolysis conditions one needs reliable structural information of the atomic architecture of the obtained nanoparticles of composition (Fe-Fe3C), in which Fe atoms have different types of the local surrounding. The latter complicates the structural characterization of samples, which was performed using the complementary methods of TEM, SAXS, XRD, XANES, and EXAFS and the results of simulations by the method of reactive force field molecular dynamics (ReaxFF MD). The size of the particles is on the order of 10 nm with cementite concentration of about 60-70 wt%. The simulations enabled to reveal that the most plausible combinations of the local structures of Fe atoms in (Fe-Fe3C) nanoparticle result in the difference of corresponding atomic pair radial distribution functions relatively to iron (RDF), which can be further filtered through the comparison with experimentally obtained RDF for iron atoms in the studied sample. Such RDF was derived from experimental Fe K-edge EXAFS in the sample by Fourier transform multi-shell processing within harmonic approximation and using the results of the analysis of SAXS, XRD, and XANES. The used approach, based on the filtering of ReaxFF MD-calculated RDFs via comparison with the EXAFS derived RDF, revealed that for particles of composition (Fe-Fe3C) with XRD derived iron:cementite ratio of ∼40:60 wt% and sizes bigger than 4 nm, the architecture with iron in core region of particle and cementite in its shell (Fe@Fe3C) is the most probable for the mean nanoparticle comparing with architectures of the inverted core-shell (Fe3C@Fe) or the mixture of iron and cementite phases (Fe+Fe3C).
BibTeX: @article{Avakyan2020, author = {Leon Avakyan and Aram Manukyan and Alena Bogdan and Harutyun Gyulasaryan and José Coutinho and Ekaterina Paramonova and Galina Sukharina and Vasiliy Srabionyan and Eduard Sharoyan and Lusegen Bugaev}, title = {Synthesis and structural characterization of iron-cementite nanoparticles encapsulated in carbon matrix}, journal = {J. Nanopart. Res.}, publisher = {Springer Science and Business Media LLC}, year = {2020}, volume = {22}, number = {1}, note = {art. no 30}, url = {http://dx.doi.org/10.1007/s11051-019-4698-8}, doi = {https://doi.org/10.1007/s11051-019-4698-8} }
Avakyan, L.A., Durimanov, V., Nemesh, D., Srabionyan, V., Ihlemann, J. and Bugaev, L.	Theoretical approach for calculation of dielectric functions of plasmonic nanoparticles of noble metals, magnesium and their alloys [Abstract] [BibTeX]	2020	Opt Mater Vol. 109, pp. 110264	article	DOI URL
Abstract: Plasmonic nanoparticles of gold, silver, their alloys, and of the promising magnesium and its alloys with noble metals, find increasing applications due to the valuable optical properties, based on the presence of localized surface plasmon resonance (LSPR) in the spectra of optical extinction. To suggest effective synthesis routes of such nanoparticles with tunable in the wide wavelength range characteristics of LSPR, it is necessary to have a reliable approach for calculation of dielectric functions for these particles with complicated atomic architecture, which can provide the description of experimental optical spectra. Such approach is also required for the implementation of the suggested earlier original technique for the solution of the inverted problem – determination of structural parameters of particles arrays from their optical spectra. With the aim to suggest such computational procedure, calculations of dielectric functions for gold, silver, magnesium and their alloys are performed using alternative density functional theory approaches: local density approximation (LDA), generalized gradient approximation (GGA) in the form of GLLBSC functional, meta-GGA in the form of TB09 potential and Hubbard-corrected local density approximation (LDA+U). Using the calculated dielectric functions, the LSPR of nanoparticles are simulated within the T-matrix approach. We show that the application of LDA+U approach is promising for the description of optical properties of bulk samples, their alloys and nanoparticles, including particles with core–shell atomic architecture. The advantage of magnesium–gold core–shell nanoparticles as a broadband nanosized plasmonic material is illustrated.
BibTeX: @article{Avakyan2020opt, author = {L. A. Avakyan and V. Durimanov and D. Nemesh and V. Srabionyan and J. Ihlemann and L. Bugaev}, title = {Theoretical approach for calculation of dielectric functions of plasmonic nanoparticles of noble metals, magnesium and their alloys}, journal = {Opt Mater}, publisher = {Elsevier BV}, year = {2020}, volume = {109}, pages = {110264}, url = {http://dx.doi.org/10.1016/j.optmat.2020.110264}, doi = {https://doi.org/10.1016/j.optmat.2020.110264} }
Srabionyan, V., Heinz, M., Kaptelinin, S.Y., Avakyan, L.A., Sukharina, G.B., Skidanenko, A.V., Pryadchenko, V., Abdulvakhidov, K.G., Mikheykin, A., Durymanov, V., Meinertz, J., Ihlemann, J., Dubiel, M. and Bugaev, L.A.	Effect of thermal post-treatment on surface plasmon resonance characteristics of gold nanoparticles formed in glass by UV laser irradiation [Abstract] [BibTeX]	2019	J. Alloys Compd. Vol. 803, pp. 354–363	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 particle's 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 sample's surface before laser irradiation was revealed.
BibTeX: @article{Srabionyan2019, author = {Vasiliy Srabionyan and Maximilian Heinz and Sviatoslav Yu Kaptelinin and Leon A. Avakyan and Galina B. Sukharina and Anna V. Skidanenko and VasiliyV. Pryadchenko and Kamal G. Abdulvakhidov and AlexeyS. Mikheykin and VeniaminA. Durymanov and Jörg Meinertz and Juergen Ihlemann and Manfred Dubiel and Lusegen A. Bugaev}, title = {Effect of thermal post-treatment on surface plasmon resonance characteristics of gold nanoparticles formed in glass by UV laser irradiation}, journal = {J. Alloys Compd.}, year = {2019}, volume = {803}, pages = {354–363}, url = {http://www.sciencedirect.com/science/article/pii/S0925838819323539}, doi = {https://doi.org/10.1016/j.jallcom.2019.06.263} }
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 [Abstract] [BibTeX]	2018	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{Avakyan2018, 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 = {2018}, volume = {30}, number = {4}, pages = {045901-045909}, url = {http://iopscience.iop.org/article/10.1088/1361-648X/aa9fcc}, doi = {https://doi.org/10.1088/1361-648X/aa9fcc} }
Heinz, M., Srabionyan, V., Avakyan, L., Bugaev, A., Skidanenko, A.V., Pryadchenko, V., Ihlemann, J., Meinertz, J., Patzig, C., Dubiel, M. and Bugev, L.	Formation and implantation of gold nanoparticles by ArF-excimer laser irradiation of gold-coated float glass [Abstract] [BibTeX]	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 Bugev, 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 = {https://doi.org/10.1016/j.jallcom.2017.11.122} }
Bugaev, A.L., Guda, A.A., Lomachenko, K.A., Shapovalov, V.V., Lazzarini, A., Vitillo, J.G., Bugaev, L.A., Groppo, E., Pellegrini, R., Soldatov, A.V., van Bokhoven, J.A. and Lamberti, C.	Core–Shell Structure of Palladium Hydride Nanoparticles Revealed by Combined X-ray Absorption Spectroscopy and X-ray Diffraction [Abstract] [BibTeX]	2017	J. Phys. Chem. C Vol. 121(33), pp. 18202-18213	article	DOI URL
Abstract: We report an in situ, temperature and H2 pressure-dependent, characterization of (2.6 ± 0.4) nm palladium nanoparticles supported on active carbon during the process of hydride phase formation. For the first time the core–shell structure is highlighted in the single-component particles on the basis of a different atomic structure and electronic configurations in the inner “core” and surface “shell” regions. The atomic structure of these particles is examined by combined X-ray powder diffraction (XRPD), which is sensitive to the crystalline core region of the nanoparticles, and by first shell analysis of extended X-ray absorption fine structure (EXAFS) spectra, which reflects the averaged structure of both the core and the more disordered shell. In the whole temperature range (0–85 °C), XRPD analysis confirms the existence of two well-separated α- and β-hydride phases with the characteristic flat plateau in the phase transition region of the pressure-lattice parameter isotherms. In contrast, first shell interatomic distances obtained from EXAFS exhibit a slope in the phase transition region, typical for nanostructured palladium. Such difference is explained by distinct properties of bulk “core” which has crystalline structure and sharp phase transition, and surface “shell” which is amorphous and absorbs hydrogen gradually without forming distinguishable α- and β-phases. Combining EXAFS and XRPD we extract, for the first time, the Pd–Pd first-shell distance in the amorphous shell of the nanoparticles, that is significantly shorter than in the bulk core and relevant in catalysis. The core/shell model is supported by the EXAFS analysis of the higher shells, in the frame of the multiple scattering theory, showing that the evolution of the third shell distance (ΔR3/R3) is comparable to the evolution of (Δa/a) obtained from XRPD since amorphous PdHx shell gives a negligible contribution in this range of distances. This operando structural information is relevant for the understanding of structure-sensitive reactions. Additionally, we demonstrate the differences in the evolution of the thermal parameters obtained from EXAFS and XRPD along the hydride phase formation.
BibTeX: @article{Bugaev2017, author = {Bugaev, Aram L. and Guda, Alexander A. and Lomachenko, Kirill A. and Shapovalov, Viktor V. and Lazzarini, Andrea and Vitillo, Jenny G. and Bugaev, Lusegen A. and Groppo, Elena and Pellegrini, Riccardo and Soldatov, Alexander V. and van Bokhoven, Jeroen A. and Lamberti, Carlo}, title = {Core–Shell Structure of Palladium Hydride Nanoparticles Revealed by Combined X-ray Absorption Spectroscopy and X-ray Diffraction}, journal = {J. Phys. Chem. C}, year = {2017}, volume = {121}, number = {33}, pages = {18202-18213}, url = {https://doi.org/10.1021/acs.jpcc.7b04152}, doi = {https://doi.org/10.1021/acs.jpcc.7b04152} }
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 [Abstract] [Comment] [BibTeX]	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.
Comment: В работе изучается два типа катализаторов, отличающиеся концентрацией платины: 4%Pt и 2%Pt.
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 = {https://doi.org/10.1021/acs.jpcc.6b09824} }
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 [Abstract] [BibTeX]	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 = {https://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\ [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1016/j.jallcom.2016.04.214} }
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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1016/j.apcata.2016.08.008} }
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 [Abstract] [Comment] [BibTeX]	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.
Comment: Платино-серебрянные нанокатализаторы с различным распределением компонент в наночастице были синтезированы методами одновременного и последовательнного восстановления ионов металлов из соответсвующих солей на углеродный носитель. Характеризация атомных структур наночастиц после приготовления и наночастиц после кислотной обработки выполнялась с помощью спектросокопии EXAFS на L3 крае поглощения Pt, с использованием методики разрешения коррелирующих параметров близколежащих координационных сфер. Влияние распределения частиц по размеру и составу на получаемые из EXAFS значения координационных чисел изучалось в данной работе путем построения серий моделей наночастиц с ГЦК симметрией, отличающихся размером, составом и формой. Для рассматриваемых распределений и полученных образцов была показана репрезнтативность моделей, построенных по данным о средних координационных числах, получаемых из EXAFS. Анализ изменения структуры по данным EXAFS, поддержаный молекулярно-динамическими расчетами с полуэмпирическим потенциалом EMT, предоставили доказательства о формировании структуры ядро-оболочка в исследуемых катализаторах.
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 = {https://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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1021/jp500734p} }
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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1016/j.jpcs.2013.12.012} }
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 [Abstract] [BibTeX]	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 = {https://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 [BibTeX]	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 = {https://doi.org/10.1007/s11051-012-0982-6} }
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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1103/PhysRevB.82.064204} }
Bugaev, L.A., Bokhoven, J.A.v., 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 [Abstract] [BibTeX]	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 Bokhoven,Jeroen A. van 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 = {https://doi.org/10.1021/jp8098285} }
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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://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 [BibTeX]	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 [Abstract] [BibTeX]	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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 [Abstract] [BibTeX]	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 [Abstract] [BibTeX]	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 [Abstract] [BibTeX]	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\ [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://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 [Abstract] [BibTeX]	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 = {https://doi.org/10.1016/0038-1098(82)90019-9} }