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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov A. N., Sukhanov A. S., Gebel S., Pavlovskii M. S., Andriushin N. D., Gao Y., Moya J. M., Morosan E., Rahn M. C.
Заглавие : Phonon softening and atomic modulations in EuAl4
Колич.характеристики :9 с
Место публикации : Phys. Rev. B. - Vol. 110, Is. 4. - Ст.045102. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.110.045102. - ISSN 24699969 (eISSN)
Примечания : Cited References: 52. - We thank Dr. Anton Kulbakov (TU Dresden) for useful discussions. The experimental work was performed at endstation ID28 of the European Synchrotron Radiation Facility (ESRF). Work at TUD was supported by the German Research Foundation (DFG) through the CRC1143 (Project-id 247310070) and the Würzburg-Dresden Cluster of Excellence ct.qmat (EXC2147, Project-id 390858490). M.C.R. is grateful for support through the Emmy-Noether programme of the DFG (Project-id 501391385). A.K. acknowledges the Education Department of the Basque Government (Grant No. PIBA_2023_1_0051). S.G. is grateful for support through a scholarship from the German Academic Exchange Service (DAAD), Project-id 57646454)
Аннотация: EuAl4 is a rare-earth intermetallic in which competing itinerant and/or indirect exchange mechanisms give rise to a complex magnetic phase diagram, including a centrosymmetric skyrmion lattice. These phenomena arise not in the tetragonal parent structure but in the presence of a charge-density wave (CDW), which lowers the crystal symmetry and renormalizes the electronic structure. Microscopic knowledge of the corresponding atomic modulations and their driving mechanism is a prerequisite for a deeper understanding of the resulting equilibrium of electronic correlations and how it might be manipulated. Here, we use synchrotron single-crystal x-ray diffraction, inelastic x-ray scattering, and lattice-dynamics calculations to clarify the origin of the CDW in EuAl4. We observe a broad softening of a transverse acoustic phonon mode that sets in well above room temperature and, at TCDW = 142 K, freezes out in an atomic displacement mode described by the superspace group Immm(00γ )s00. In the context of previous work, our observation is a clear confirmation that the CDW in EuAl4 is driven by electron-phonon coupling. This result is relevant for a wider family of BaAl4 and ThCr2Si2- type rare-earth intermetallics known to combine CDW instabilities and complex magnetism.
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2.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I.
Заглавие : The interplay of phonon and magnetic mechanism of pairing in strongly correlated electron system of high-Tc cuprates
Коллективы : International Conference on New Theoreties, Discoveries & Applications of Superconductors and Related Materials, Zhongguancun International Consortium of R&D of Superconductivity Technology Inaugurating Meeting
Место публикации : Seventh International Conference on New Theoreties, Discoveries & Applications of Superconductors and Related Materials and Zhongguancun International Consortium of R&D of Superconductivity Technology Inaugurating Meeting: May 13-16, 2009, Beijing, China. - Ст.S1E0900
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3.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Rasch J. C. E., Böhm M., Schefer J., Mutka H., Abramova M. G. , Vasilyeva I.
Заглавие : Spin-phonon coupling in CuCrS2 probed by inelastic neutron scattering
Коллективы : DPG - spring meeting of the Division Condensed Matter
Место публикации : DPG (Deutsche Physicalische Gesellschaft) Spring Meeting: Dresden, 22nd - 27th of March, 2009. - Ст.Th-D-2.4-06. - С. 367
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I.
Заглавие : Lattice source for charge and spin inhomogeneity in 2D perovskite cuprates
Колич.характеристики :5 с
Место публикации : Phys. B: Condens. Matter. - 2024. - Vol. 673. - Ст.415457. - ISSN 09214526, DOI 10.1016/j.physb.2023.415457. - ISSN 18732135
Примечания : Cited References: 31. - We acknowledge the support of the Russian Science Foundation through grant RSF No. 22-22-00298
Аннотация: In the work we highlight the structural features of 2D perovskite cuprates (tilted CuO6 octahedra with different orientation with respect to spacer rocksalt layers), where sources of charge and spin inhomogeneity can be hidden. We used the impurity Anderson model with the Jahn–Teller(JT) local cells to show the charge inhomogeneity arises at any low doping concentration x, but disappears when the doping level exceeds threshold concentration xc, and the smaller the magnitudes xc, the larger the area of regions with JT pseudo effect. It is expected that spontaneous chiral symmetry breaking in the dynamic JT state of the stripe CuO2 layer as a whole can lead to the appearance of the goldstone phonon mode. As consequence, the giant thermal Hall effect could be observed in the 2D perovskite cuprates with CuO6 octahedra, rather than with CuO4 squares, e.g. in the Tl-based n layer cuprates or cuprates based on infinite-layer CaCuO2 structure.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chernyshev V. A., Ruseikina A. V., Grigoriev M. V., Krylova S. N., Safin D. A.
Заглавие : First-principles calculations to investigate optical, phonon and electronic properties of quaternary sulfides SrRECuS3 (RE = La, Nd, Tm)
Колич.характеристики :7 с
Место публикации : Inorg. Chem. Commun. - 2024. - Vol. 165. - Ст.112449. - ISSN 13877003 (ISSN), DOI 10.1016/j.inoche.2024.112449. - ISSN 18790259 (eISSN)
Примечания : Cited References: 43. - This work was supported by The Ministry of Science and Higher Education of the Russian Federation (project No. FEUZ-2023-0017)
Аннотация: The structure and properties of three layered heterometallic quaternary sulfides SrLaCuS3, SrNdCuS3 and SrTmCuS3 were studied for the first time using first-principles calculations in the stoichiometric and nonstoichiometric approximations. The applied DFT-based computations were performed using a hybrid functional with the contribution of nonlocal exchange in the Hartree-Fock formalism. It was revealed that the nonstoichiometry of SrLaCuS3 and SrNdCuS3 must be considered for modeling phonon spectra, elastic properties and band gaps. The wavenumbers and types of the Raman and "silent" modes at the Г-point were determined. From the analysis of displacement vectors, the degree of participation of ions in each mode was determined. The elastic constants and elastic moduli of the reported sulfides were calculated.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Andriushin N. D., Sukhanov A. S., Korshunov A. N., Pavlovskii M. S., Rahn M. C., Nikitin S. E.
Заглавие : Phonon topology and winding of spectral weight in graphite
Колич.характеристики :6 с
Место публикации : Phys. Rev. Lett. - 2023. - Vol. 131, Is. 24. - Ст.246601. - ISSN 00319007 (ISSN), DOI 10.1103/PhysRevLett.131.246601. - ISSN 10797114 (eISSN)
Примечания : Cited References: 42. - We thank R. Coldea for stimulating discussions. A. Bosak participated in the discussion and preparation of the experiment. We acknowledge financial support from the Swiss National Science Foundation, from the European Research Council under the grant Hyper Quantum Criticality (HyperQC), the German Research Foundation (DFG) through the Collaborative Research Center SFB 1143 (Project No. 247310070), and from the European Union Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant No. 884104. We acknowledge the European Synchrotron Radiation Facility (ESRF) for provision of synchrotron radiation facilities
Аннотация: The topology of electronic and phonon band structures of graphene is well studied and known to exhibit a Dirac cone at the K point of the Brillouin zone. Here, we applied inelastic x-ray scattering (IXS) along with ab initio calculations to investigate phonon topology in graphite, the 3D analog of graphene. We identified a pair of modes that form a very weakly gapped linear anticrossing at the K point that can be essentially viewed as a Dirac cone approximant. The IXS intensity in the vicinity of the quasi-Dirac point reveals a harmonic modulation of the phonon spectral weight above and below the Dirac energy, which was previously proposed as an experimental fingerprint of the nontrivial topology. We illustrate how the topological winding of IXS intensity can be understood in terms of atomic displacements and highlight that the intensity winding is not in fact sensitive in telling quasi- and true Dirac points apart.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylova S. N.
Заглавие : Calculation of the phonon spectrum of PbMnBO4 crystal using density functional theory
Колич.характеристики :9 с
Место публикации : Crystallogr. Rep. - 2023. - Vol. 68, Is. 5. - P.788-796. - ISSN 10637745 (ISSN), DOI 10.1134/S1063774523600436. - ISSN 1562689X (eISSN)
Примечания : Cited References: 31. - This study was supported by the Russian Foundation for Basic Research, project no. 21-52-12018 NNIO_а
Аннотация: The phonon dispersion and Raman spectrum of the PbMnBO4 ferromagnetic crystal have been calculated within the density functional theory. Imaginary phonon branches have been observed at the points Y, Z, and Г and along the X–S direction of the Brillouin zone, which indicates structural instability and a possible phase transition with variation in external factors (temperature and pressure). The shapes of vibrations and symmetry types of the normal modes of the crystal at the center of the Brillouin zone have been determined. The calculation results are compared with the experimental and theoretical spectra from other studies. It is shown that the vibrational mode of highest intensity at 692.5 cm–1 in the spectrum and the mode at 272.3 cm–1, corresponding to the experimental modes at 690.5 and 224.7 cm–1, are bending vibrations of oxygen atoms in distorted MnO6 octahedra.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Oreshonkov A. S., Sukhanova E. V., Popov Z. I.
Заглавие : Phonon dynamics in MoSi2N4: insights from DFT calculations
Колич.характеристики :11 с
Место публикации : Phys. Chem. Chem. Phys. - 2023. - Vol. 25, Is. 43. - P.29831-29841. - ISSN 14639076 (ISSN), DOI 10.1039/D3CP02921B. - ISSN 14639084 (eISSN)
Примечания : Cited References: 74. - The authors acknowledge financial support from Russian Science Foundation (project №21-73-20183, https://rscf.ru/project/21-73-20183/)
Аннотация: We have reported the density functional theory investigations on the monolayer, 2 layered and bulk MoSi2N4 in three structural modifications called as α1 [Science, DOI: 10.1126/science.abb7023], α2 and α3 [Adv. Funct. Mater., DOI: 10.1002/adfm.202214050]. We showed that in the case of monolayers the difference in total energies is less than 0.1 eV between α1 and α3 phases, and less than 0.2 eV between α1 and α2 geometries. The most energetically favorable layer stacking for the bulk structures of each phase was investigated. All considered modifications are dynamically stable from a single layer to a bulk structure in energetically favorable stacking. Raman spectra for the monolayer, 2 layered and bulk structures were simulated and the vibrational analysis was performed. The main difference between in the obtained spectra is associated with the position of the strongest band which depends on the Mo-N bond length. According to the obtained data, we can conclude that Raman line at 348 cm–1 in the experimental spectra of MoSi2N4, can have more complex explanation then just Γ-point Raman-active vibration as was discussed before in [Science, DOI: 10.1126/science.abb7023].
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hoffman A. E.J., Senkovska I., Wieme J., Krylov A. S., Kaskel S., Van Speybroeck V.
Заглавие : Unfolding the terahertz spectrum of soft porous crystals: rigid unit modes and their impact on phase transitions
Место публикации : J. Mater. Chem. A. - 2022. - Vol. 10, Is. 33. - P.17254-17266. - ISSN 20507488 (ISSN), DOI 10.1039/d2ta01678h
Примечания : Cited References: 80. - This work was financially supported by the Fund for Scientific Research Flanders (FWO), the Research Board of the Ghent University (BOF), the Deutsche Forschungsgemeinschaft (DFG, project number 448809307), and the Russian Foundation for Basic Research (RFBR, project number 21-52-12018). The authors thank Kerstin Zechel for sample synthesis. The computational resources and services used in this work were provided by the Flemish Supercomputer Center (VSC), funded by FWO and the Flemish Government
Аннотация: Phase transitions in flexible metal-organic frameworks or soft porous crystals are mediated by low-frequency phonons or rigid-unit modes. The alteration of specific building blocks may change the lattice dynamics of these frameworks, which can influence the phase transition mechanism. In this work, the impact of building block substitution on the rigid-unit modes in flexible MIL-53 analogs with a winerack topology will be investigated via ab initio lattice dynamics calculations. First, the accuracy of the theoretical simulations is verified via experimental Raman measurements, which provide unique fingerprint vibrations in the terahertz range to characterize the phase transition. Following analysis of the low-frequency vibrations shows that there exists a set of universal rigid-unit modes inducing translations and/or rotations of the building blocks. The theoretical results demonstrate that linker substitutions have a large effect on the rigid-unit mode frequencies, whereas this is less so for inorganic chain substitutions. These findings may help to rationally tune the phonon frequencies in soft porous crystals.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Dudnikov V. A., Sokolov A. Е., Ovchinnikova T. M., Shestakov N. P., Ovchinnikov S. G.
Заглавие : Fluctuations of the multiplicity of Co3+ ions and softening of the phonon spectrum of rare-earth cobalt oxides
Место публикации : JETP Letters. - 2022. - Vol. 115, Is. 10. - P.615-619. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364022100575
Примечания : Cited References: 25. - This work was supported by the Russian Science Foundation (project no. 18-12-00022)
Аннотация: An unconventional temperature dependence of infrared absorption spectra of rare-earth cobalt oxides LaCoO3 and GdCoO3 has been studied experimentally and theoretically in the temperature range of 3.2–550 K. A quite strong softening of the optical phonon mode has been detected, which cannot be explained by standard lattice anharmonicity. It has been shown that the redshift of the phonon spectrum is due to the e-lectron–phonon coupling quadratic in the lattice displacement and to fluctuations of the multiplicity of Co3+ ions.
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11.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Hoffman A. E. J., Senkovska I., Krylov A. S., Kaskel S., Speybroeck V. V.
Заглавие : Unfolding the terahertz spectrum of soft porous crystals: rigid unit modes and their impact on phonon properties
Коллективы : International Conference on Metal-Organic Frameworks and Open Frameworks Compounds
Место публикации : International Conference on Metal-Organic Frameworks and Open Frameworks Compounds (MOF 2022): book of abstracts. - 2022. - P.254
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Kuz'min V. I., Ovchinnikov S. G.
Заглавие : Effect of the electron-phonon interaction on the formation of the exciton phase in strongly correlated systems with the spin crossover
Коллективы : Российская академия наук, Физико-технический институт им. Е.К. Завойского ФИЦ Казанского научного центра РАН, Казанский (Приволжский) федеральный университет, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : VIII Euro-Asian symposium "Trends in magnetism" (EASTMAG-2022): Book of abstracts/ program com. S. G. Ovchinnikov [et al.]. - 2022. - Vol. 2, Sect. H: Magnetism of strongly correlated electron systems. - Ст.H.P15. - P.104-105. - ISBN 978-5-94469-051-7
Примечания : Cited References: 4. - The study was supported by the Russian Scientiʅc Foundation, the Krasnoyarsk Regional Fund of Science, grant No. 22-22-20007
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Tanwar M., Pathak D. K., Chaudhary A., Krylov A. S., Pfnur H., Sharma A., Ahn B., Lee S., Kumar R.
Заглавие : Pseudo-anomalous size-dependent electron-phonon interaction in graded energy band: Solving the Fano paradox
Место публикации : J. Phys. Chem. Lett. - 2021. - Vol. 12, Is. 8. - P.2044-2051. - ISSN 19487185 (ISSN), DOI 10.1021/acs.jpclett.1c00217
Примечания : Cited References: 77
Аннотация: Quantum size effects on interferons (electron-phonon bound states), confined in fractal silicon (Si) nanostructures (NSs), have been studied by using Raman spectromicroscopy. A paradoxical size dependence of Fano parameters, estimated from Raman spectra, has been observed as a consequence of longitudinal variation of nanocrystallite size along the Si wires leading to local variations in the dopants' density which actually starts governing the Fano coupling, thus liberating the interferons to exhibit the typical quantum size effect. These interferons are more dominated by the effective reduction in dopants' density rather than the quantum confinement effect. Detailed experimental and theoretical Raman line shape analyses have been performed to solve the paradox by establishing that the increasing size effect actually is accompanied by receding Fano coupling due to the weakened electronic continuum. The latter has been validated by observing a consequent variation in the Raman signal from dopants which was found to be consistent with the above conclusion.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Zotova M. V., Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Phonon-assisted insulator-metal transitions in correlated systems driven by doping
Место публикации : Phys. Rev. B. - 2021. - Vol. 104, Is. 15. - Ст.155153. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.104.155153
Примечания : Cited References: 63. - The reported study was funded by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, and Krasnoyarsk Regional Fund of Science according to the research project “Studies of superexchange and electron-phonon interactions in correlated systems as a basis for searching for promising functional materials”, No. 20-42-240016
Аннотация: We consider how electron-phonon interaction influences the insulator-metal transitions driven by doping in a strongly correlated system. Using the polaronic version of the generalized tight-binding method, we investigate a multiband two-dimensional model taking into account both charge density displacement and transitive types of electron-lattice contributions. For adiabatic ratio t≫ω0, we analyze a wide electron-phonon parameter range and demonstrate the relationship between transition features and such properties of the system as polaron and bipolaron crossovers, the redistribution of the spectral weight due to the multiparticle effects of Coulomb and electron-phonon interactions, orbital selectivity, flat-band formation, and pseudogap behavior of various origins.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Nikolaev S. V., Zotova M. V., Kaldin R. A., Ovchinnikov S. G.
Заглавие : Polaron transformations in the realistic model of the strongly correlated electron system
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science [18-42-240017, 19-42240007]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 23. - Ст.235114. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.235114. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 69. - We acknowledge the stimulating discussions with V. A. Gavrichkov, G. Seibold, and K. I. Kugel. The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science according to the research project "Features of electron-phonon coupling in high-temperature superconductors with strong electronic correlations" No. 18-42-240017 and project "Electronic correlation effects and multiorbital physics in iron-based materials and cuprates" No. 19-42240007.
Предметные рубрики: ANOMALOUS-DISPERSION
PHONON INTERACTION
PHASE-TRANSITIONS
LO PHONONS
Аннотация: Electron-phonon coupling, diagonal in a real space formulation, leads to a polaron paradigm of smoothly varying properties. However, fundamental changes, namely the singular behavior of polarons, occur if off-diagonal pairing is involved into consideration. The study of polaron transformations and related properties of matter is of particular interest for realistic models, since competition between diagonal and off-diagonal electron-phonon contributions in the presence of other strong interactions can result in unconventional behavior of the system. Here we consider a two-dimensional multiband pd model of cuprate superconductors with electron-phonon interaction and analyze the features of the systems that are caused by the competition of diagonal and off-diagonal electron-phonon contributions in the limit of strong electron correlations. Using the polaronic version of the generalized tight-binding method, we describe the evolution of the band structure, Fermi surface, density of states at Fermi level, and phonon spectral function in the space of electron-phonon parameters ranging from weak to strong coupling strength of the adiabatic limit. On the phase diagram of polaron properties we reveal two quantum phase transitions and show how electron-phonon interaction gives rise to Fermi surface transformation (i) from hole pockets to true Fermi arcs and (ii) from hole to electron type of conductivity. We also demonstrate the emergence of new states in the phonon spectral function of the polaron and discuss their origin.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Gudim I. A., Vtyurin A. N.
Заглавие : Soft modes in HoFe2.5Ga0.5(BO3)4 solid solution
Коллективы : European Meeting on Ferroelectricity , Russian Foundation for Basic Research GrantRussian Foundation for Basic Research (RFBR) [1802-00754]
Место публикации : Ferroelectrics. - 2020. - Vol. 556, Is. 1. - P.16-22. - ISSN 0015-0193, DOI 10.1080/00150193.2020.1713334. - ISSN 1563-5112(eISSN)
Примечания : Cited References: 14. - This work was supported by the Russian Foundation for Basic Research Grant No 1802-00754.
Предметные рубрики: RAMAN-SCATTERING
SPECTRA
HO1-XNDXFE3(BO3)(4)
Аннотация: The condensation of two soft modes has been found when studying the Raman spectra of the solid solution HoFe2.5Ga0.5(BO3)4 in the temperature range from 7 to 350 K. The first high-temperature soft mode is associated with the structural phase transition from the R32 phase to the P3121 phase. The second soft mode is related to the reveal of the phonon-magnon interaction during magnetic ordering in the crystal. The temperatures of the structural phase transition T1 = 266 K and the magnetic phase transition T2 = 28 K are established. Experimentally interaction between the structural phase transition order parameter fluctuations and the magnetic order parameter fluctuations was found.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Oreshonkov A. S., Roginskii E. M., Atuchin V. V.
Заглавие : New candidate to reach Shockley–Queisser limit: The DFT study of orthorhombic silicon allotrope Si(oP32)
Место публикации : J. Phys. Chem. Solids. - 2020. - Vol. 137. - Ст.109219. - ISSN 00223697 (ISSN), DOI 10.1016/j.jpcs.2019.109219
Примечания : Cited References: 44. - The authors are grateful for the support from RFBR , according to the research projects 18-03-00750 and 18-32-20011 . The computations were performed using the facilities of the Computational Center of the Research Park of St. Petersburg State University. This study was also supported by the Russian Science Foundation (project 19-42-02003 , in part of conceptualization).
Аннотация: In the present study, the unit cell parameters and atomic coordinates are predicted for the Pbcm orthorhombic structure of Si(oP32) modification. This new allotrope of silicon is mechanically stable and stable with respect to the phonon states. The electronic structure of Si(oP32) is calculated for LDA and HSE06 optimized structures. The band gap value Eg = 1.361 eV predicted for Si(oP32) is extremely close to the Shockley–Queisser limit and it indicates that the Si(oP32) modification is a promising material for efficient solar cells. The frequencies of Raman and Infrared active vibrations is calculated for allotrope Si(oP32).
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Sokolov A. Е., Dudnikov V. A., Shulga K. V., Volochaev M. N., Zharkov S. M., Shestakov N. P., Vysotin M. A., Ovchinnikov S. G.
Заглавие : Contribution of the multiplicity fluctuation in the temperature dependence of phonon spectra of rare-earth cobaltites
Место публикации : Molecules. - 2020. - Vol. 25, Is. 18. - Ст.4316. - ISSN 14203049 (ISSN), DOI 10.3390/molecules25184316
Примечания : Cited References: 34. - This work was supported by the Russian Science Foundation grant 18-02-00022. The scanning electron microscopy investigations were conducted in the SFU Joint Scientific Center, supported by the State assignment (#FSRZ-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation. The other research was carried out at the Krasnoyarsk Regional Center of Research Equipment of the Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: We have studied, both experimentally and theoretically, the unusual temperature dependence of the phonon spectra in NdCoO3, SmCoO3 and GdCoO3, where the Co3+ ion is in the low-spin (LS) ground state, and at the finite temperature, the high-spin (HS) term has a nonzero concentration nHS due to multiplicity fluctuations. We measured the absorption spectra in polycrystalline and nanostructured samples in the temperature range 3–550 K and found a quite strong breathing mode softening that cannot be explained by standard lattice anharmonicity. We showed that the anharmonicity in the electron–phonon interaction is responsible for this red shift proportional to the nHS concentration.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu, Youquan, Mei, Dajiang, Wang, Naizheng, Molokeev M. S., Jiang, Xingxing, Lin, Zheshuai
Заглавие : Intrinsic isotropic near-zero thermal expansion in Zn4B6O12X (X = O, S, Se)
Место публикации : ACS Appl. Mater. Interfaces. - 2020. - Vol. 12, Is. 34. - P.38435-38440. - ISSN 1944-8244, DOI 10.1021/acsami.0c12351. - ISSN 1944-8252(eISSN)
Примечания : Cited References: 43. - This work was supported by the National Scientific Foundations of China (Grants 51872297, 51702330, 11974360, 51972208, 51890864, and 51802321), Russian Foundation for Basic Research (Grant 17-52-53031), and Fujian Institute of Innovation (FJCXY18010201) in CAS. X.J. acknowledges the support from the Youth Innovation Promotion Association in CAS (Grant 2017035) and Youth Talent Promotion Project from China Association for Science and Technology
Предметные рубрики: CRYSTAL
Аннотация: Zero thermal expansion (ZTE) materials, keeping size constant as temperature varies, are valuable for resisting the deterioration of the performance from environmental temperature fluctuation, but they are rarely discovered due to the counterintuitive temperature-size effect. Herein, we demonstrate that a family of borates with sodalite cage structure, Zn4B6O12X (X = O, S, Se), exhibits intrinsic isotropic near-ZTE behaviors from 5 to 300 K. The very low thermal expansion is mainly owing to the coupling rotation of [BO4] rigid groups constrained by the bonds between Zn and cage-edged O atoms, while the central atoms in the cage have a negligible contribution. Our study has significant implications on the understanding of the ZTE mechanism and exploration of new ZTE materials.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Makarov I. A., Zotova M. V., Ovchinnikov S. G.
Заглавие : Influence of the diagonal and off-diagonal electron-phonon interactions on the formation of local polarons and their band structure in materials with strong electron correlations
Коллективы : Russian Foundation for Basic Research [16-02-00098]; Basic Research Program of the Presidium of the Russian Academy of Sciences [12]
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 126, Is. 5. - P.683-698. - ISSN 1063-7761, DOI 10.1134/S1063776118050059. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 58. - We are grateful to V.I. Zinenko and V.A. Gavrichkov for useful discussions. This work was financially supported by the Russian Foundation for Basic Research (project no. 16-02-00098) and the Basic Research Program no. 12 of the Presidium of the Russian Academy of Sciences ("Fundamental Problems of High-Temperature Superconductivity").
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
D-WAVE SUPERCONDUCTIVITY
LATTICE
Аннотация: For systems with strong electron correlations and strong electron–phonon interaction, we analyze the electron–phonon interaction in local variables. The effects of the mutual influence of electron–electron and electron–phonon interactions that determine the structure of local Hubbard polarons are described. Using a system containing copper–oxygen layers as an example, we consider the competition between the diagonal and off-diagonal interactions of electrons with the breathing mode as the polaron band structure is formed within a corrected formulation of the polaron version of the generalized tight-binding method. The band structure of Hubbard polarons is shown to depend strongly on the temperature due to the excitation of Franck–Condon resonances. For an undoped La2CuO4 compound we have described the evolution of the band structure and the spectral function from the hole dispersion in an antiferromagnetic insulator at low temperatures with the valence band maximum at point (π/2, π/2) to the spectrum with the maximum at point (π, π) typical for the paramagnetic phase. The polaron line width at the valence band top and its temperature dependence agree qualitatively with angle-resolved photoemission spectroscopy for undoped cuprates.
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