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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Theory of an Fm3m - I4/m structural phase transition in an Rb2KScF6 crystal
Разночтения заглавия :us: Theory of an Fm3mI4/m Structural Phase Transition in an Rb2KScF6 Crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2000. - Vol. 91, Is. 2. - P314-323. - ISSN 1063-7761, DOI 10.1134/1.1311990
Примечания : Cited References: 16
Предметные рубрики: FIRST-PRINCIPLES THEORY
LATTICE-DYNAMICS
PEROVSKITES
ELPASOLITES
Аннотация: An Rb2KScF6 crystal having an elpasolite structure undergoes a sequence of Fm3m -- I4/m -- P12(1)/n1 structural phase transitions where the transition to the tetragonal phase is associated with "rotation" of the ScF6 octahedron. An effective Hamiltonian is constructed to describe the Fm3m -- I4/m transition using the approximation of a local mode for which we selected a "soft mode" whose eigenvector corresponds to the rotation of the octahedron. The effective Hamiltonian also includes the relationship between the local mode and the homogeneous elastic strains. The parameters of the effective Hamiltonian were determined using the generalized Gordon-Kim model of an ionic crystal which allows for the deformability and polarizability of the ions. The thermodynamic properties of a system with this model Hamiltonian were investigated using the Monte Carlo method. The calculated phase transition temperature of 250 K is almost the same as the experimental value (252 K). The tetragonal phase remains stable as far as T = 0 K and a second transition (to the monoclinic phase) cannot be obtained using this effective Hamiltonian. This suggests that if the transition to the tetragonal phase is mainly associated with "rotations" of the octahedrons, in order to describe the phase transition to the monoclinic phase the effective Hamiltonian must allow for additional degrees of freedom mainly associated with the motion of rubidium ions. (C) 2000 MAIK "Nauka/Interperiodica".
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Lattice dynamics and statistical mechanics of the Fm3m - I4/m structural phase transition in Rb2KInF6
Разночтения заглавия :авие SCOPUS: Lattice dynamics and statistical mechanics of the Fm3m I4/m structural phase transition in Rb2KInF6
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2001. - Vol. 43, Is. 12. - P2290-2300. - ISSN 1063-7834, DOI 10.1134/1.1427959
Примечания : Cited References: 18
Предметные рубрики: FIRST-PRINCIPLES THEORY
RB2KSCF6 CRYSTAL
ELPASOLITES
PEROVSKITES
Аннотация: The static and dynamic properties of cubic Rb2KInF6 crystals with elpasolite structure are calculated using a nonempirical method. Calculations are performed within a microscopic ionic-crystal model taking into account the deformation and polarization of ions. The deformation parameters of ions are determined by minimizing the total energy of the crystal. The calculated equilibrium lattice parameters agree satisfactorily with the experimental data. It is found that in the cubic phase there are vibrational modes that are unstable everywhere in the Brillouin zone. The eigenvectors of the unstablest mode at the center of the Brillouin zone of the cubic phase are associated with the displacements of F ions and correspond to rotations of InF6 octahedra. Condensation of this mode leads to a tetragonal distortion of the structure. In order to describe the Fm3m -- I4/m phase transition, an effective Hamiltonian is constructed under the assumption that the soft mode whose eigenvector corresponds to octahedron rotation is local and coupled with homogeneous elastic strains. The parameters of the effective Hamiltonian are determined using the calculated crystal energy for the distorted structures due to soft-mode condensation. The thermodynamic properties of the system with this model Hamiltonian are investigated using the Monte Carlo method. The phase transition temperature is calculated to be 550 K, which is twice its experimental value (283 K). The tetragonal phase remains stable down to T = 0 K; the effective Hamiltonian used in this paper thus fails to describe the second phase transition (to the monoclinic phase). Thus, the transition to the tetragonal phase occurs for the most part through octahedron rotations; however, additional degrees of freedom, first of all, the displacements of Rb ions, should be included into the effective Hamiltonian in order to describe the transition to the monoclinic phase. (C) 2001 MAIK "Nauka/ Interperiodica".
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GOREV M. V., FLEROV I. N., VORONOV V. N., TRESSO A., GRANNEK J., GHAMINADE J. P.
Заглавие : THERMOPHYSICAL STUDIES OF THE RB2KFEF6 FERROELASTIC
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1994. - Vol. 36, Is. 4. - P1121-1125. - ISSN 0367-3294
Примечания : Cited References: 15
Предметные рубрики: STRUCTURAL PHASE-TRANSITIONS
RB2KMIIIF6 ELPASOLITES
DIAGRAMS
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GOREV M. V., MISYUL S. V., BOVINA A. F., ISKORNEV I. M., KOKOV I. T., FLEROV I. N.
Заглавие : THERMODYNAMIC PROPERTIES OF ELPASOLITES CS2NANDCL6 AND CS2NAPRCL6
Разночтения заглавия :авие SCOPUS: Thermodynamic properties of elpasolites Cs 2NaNdCl 6 and Cs 2NaPrCl 6
Место публикации : JOURNAL OF PHYSICS C-SOLID STATE PHYSICS: IOP PUBLISHING LTD, 1986. - Vol. 19, Is. 14. - P2441-2447. - ISSN 0022-3719, DOI 10.1088/0022-3719/19/14/010
Примечания : Cited References: 20
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Voronov V. N., Bovina A. F.
Заглавие : Thermodynamic characteristics and phase transitions in Rb3B3+F6 (B3+=Ga, DY) cryolite fluoride crystals
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1996. - Vol. 38, Is. 7. - P2203-2213. - ISSN 0367-3294
Примечания : Cited References: 26
Предметные рубрики: HYDROSTATIC-PRESSURE
ELPASOLITES
CS2RBDYF6
RB2KFEF6
DIAGRAMS
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6.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vtyurin A. N., Krylov A. S., Krylova S. N., Gerasimova J. V., Ivanenko A. A., Voronov V. N.
Заглавие : Temperature phase transitions in Rb2KRe3+F6 elpasolites
Место публикации : Perovskites and other framework structure crystalline materials: 2d-perovskites, aurivillius, ruddlesden-popper, dion-jacobson phases, tungsten bronzes, clays, and others: Collaborating Academics, 2021. - P.309-326. - (Artificially created materials and applications; Vol. 1)
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bovina A. F., Chernenko T. V., Tressand A., Grannes J.
Заглавие : T-x phase diagram of mixed elpasolites Rb2KGaxSc1-xF6
Коллективы : International Seminar on Physics of Ferroelastics
Место публикации : Izv. Akad. Nauk Ser. Fiz./ International Seminar on Ferroelastic (7 ; Jun, 1997 ; Kazan, Russia). - 1998. - Vol. 62, Is. 8. - P.1532-1536. - ISSN 1026-3489
Примечания : Cited References: 12
Предметные рубрики: RB2KMIIIF6 ELPASOLITES
TRANSITIONS
FERROELASTICS
RB2KFEF6
WOS
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Melnikova S. V., Misyul S. V., Voronov V. N., Aleksandrov K. S., Tressaud A., Grannec J., Shaminade J. P., Rabardel L., Guingard H.
Заглавие : Study of the Fm3m-]14/m-]P21/n successive phase-transitions in Rb2KINF6 and Rb2KLUF6 elpasolites
Место публикации : Fiz. Tverd. Tela: Mezhdunarodnaya kniga, 1992. - Vol. 34, Is. 11. - P.3493-3500. - ISSN 0367-3294
Примечания : Cited References: 13
Предметные рубрики: THERMODYNAMIC PROPERTIES
RB2KMIIIF6 ELPASOLITES
WOS
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GOREV M. V., BOVINA A. F., BONDARENKO G. V., FLEROV I. N., TRESSO A., GRANNEK Z.
Заглавие : STUDY OF RB2KSC1-XGAXF6 SOLID-SOLUTIONS
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1995. - Vol. 37, Is. 3. - P819-823. - ISSN 0367-3294
Примечания : Cited References: 12
Предметные рубрики: STRUCTURAL PHASE-TRANSITIONS
RB2KMIIIF6 ELPASOLITES
DIAGRAMS
WOS
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Safonov I. N., Misyul' S. V., Molokeev M. S., Ivliev M. P.
Заглавие : Structural transformations and phenomenological description of the formation of phase states in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb)
Коллективы : Ministry of Education and Science of the Russian Federation [3.2534.2014/K]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 3. - P.491-498. - ISSN 1063, DOI 10.1134/S1063783415030282. - ISSN 10906460(eISSN)
Примечания : Cited References:20. - This study was supported by the Ministry of Education and Science of the Russian Federation within the framework of the State Task for the Russian Siberian Federal University for Implementation of Scientific Research Work in 2014 (assignment no. 3.2534.2014/K).
Предметные рубрики: TRANSITIONS
CRYSTALS
Аннотация: The structures of the cubic and monoclinic phases of an Rb2KHoF6 crystal from a series of elpasolites Rb2KB′F6 (B′ = Ho, Dy, Tb), which undergoes a trigger phase transition, have been investigated using X-ray powder diffraction. The critical and noncritical displacements of atoms in the Rb2KHoF6 structure have been determined from the group-theoretical analysis of the complete condensate of order parameters. It has been reliably established that a change in the symmetry due to the phase transition in this crystal can be represented in the form Fmˉ3m11−9(Γ+4)⊕10−3(X+3)(ϕ,ϕ,ψ)P121/n1Fm\bar 3m\frac{{11 - 9(\Gamma _4. + ) \oplus 10 - 3(X_3. + )}} {{(\phi ,\phi ,\psi )}}P12_1 /n1 . A phenomenological analysis of the conditions responsible for the formation of phase states upon the phase transitions in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb) has been carried out. Taking into account the structural data and using the phenomenological theory, it has been found that the main factor determining the formation of phase states in these and related crystals is the instability of the elpasolite structure with respect to rotational distortions of two types. It has been shown that an important role in the formation of a sequence of structural transformations in these crystals is played by the interaction of rotational order parameters and displacements of the cation from the center of a cuboctahedral hole.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Voronov V. N., Gorev M. V., Melnikova S.V., Misyul S. V., Flerov I. N.
Заглавие : Structural phase-transitions in Rb2KHOF6 and Rb2KTBF6 elpasolites
Место публикации : Fiz. Tverd. Tela. - 1991. - Vol. 33, Is. 10. - P.2945-2947. - ISSN 0367-3294
Примечания : Cited References: 9
Предметные рубрики: MODE
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Beznosikov B. V., Flerov I. N., Gorev M. V., Melnikova S.V., Misyul S. V., Voronov V. N.
Заглавие : Structural phase-transitions in elpasolites Rb2NaDYF6 and Rb2KDYF6
Место публикации : Ferroelectr. Lett. Sect. - 1983. - Vol. 1, Is. 2. - P.35-41. - ISSN 0731-5171
Примечания : Cited References: 12
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gerasimova J. V., Vtyurin A. N., Ivanenko A. A., Shestakov N. P.
Заглавие : Spectroscopy study of A2A'MO3F3 cryolites-elpasolites
Коллективы : Russia/CIS/Baltic/Japan Symposium on Ferroelectricity
Место публикации : Abstracts of the 10th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity. - 2010. - P.97
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Vtyurin A. N., Gerasimova J. V., Krylov A. S., Laptash N. M., Voyt E. I., Kocharova A. G., Surovtsev S. V.
Заглавие : Raman spectra and ordering processes in alcaline-tungsten oxyfluorides
Коллективы : Russian-CIS-Baltic-Japanese symposium on ferroelectricity
Место публикации : Ferroelectrics: Taylor & Francis LTD, 2007. - Vol. 347. - P.79-85. - ISSN 0015-0193, DOI 10.1080/00150190601187070
Примечания : Cited References: 8
Предметные рубрики: PHASE-TRANSITIONS
ELPASOLITES
Аннотация: Raman spectra of perovskite-like (NH4)(3)WO3F3 (assigned below as A3), (NH4)(2)KWO3F3 (A2K), Cs-2(NH4)WO3F3 (C2A) oxyfluorides are obtained in a wide temperature range including transition points for A3 and A2 K crystals. Transition anomalies are found and analyzed. Transformation in A3 crystal is shown to be bound with octahedron groups ordering and H-bond formation, that is accompanied by cell volume multiplication, hardening and formation of complex discrete low frequency lattice spectrum. Same cell doubling was found in A2 K crystal, but without lattice ordering. C2A lattice stays disordered down to 15 K.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Melnikova S. V., Misyul S. V., Voronov V. N., Aleksandrov K. S.
Заглавие : Phase-transitions in elpasolite Rb2KSCF6
Место публикации : Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 7. - P.2185-2195. - ISSN 0367-3294
Примечания : Cited References: 24
Предметные рубрики: RB2KMIIIF6 ELPASOLITES
CS2NANDCL6
SCATTERING
RB2NADYF6
CS2RBDYF6
RB2KDYF6
CRYSTAL
MODE
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Aleksandrov K. S., Tressaud A., Grannec J., Couzi M.
Заглавие : Phase transitions in elpasolites (ordered perovskites)
Место публикации : Materials Science and Engineering R: Reports. - 1998. - Vol. 24, Is. 3. - P.81-151. - ISSN 0927-796X
Примечания : Cited References: 174
Предметные рубрики: ELASTIC NEUTRON-DIFFRACTION
MII = CO
RAMAN-SCATTERING
THERMODYNAMIC PROPERTIES
CRYSTAL-STRUCTURE
SINGLE-CRYSTALS
RB2KMIIIF6 ELPASOLITES
CUBIC PEROVSKITES
TEMPERATURE FORM
HIGH-RESOLUTION
Ключевые слова (''Своб.индексиров.''): crystal atomic structure--crystal growth--crystal lattices--crystallization--crystallography--ferroelectricity--hydrostatic pressure--order disorder transitions--single crystals--thermodynamics--elpasolites--landau theory--perovskite
Аннотация: Many compounds with general chemical formula A2BB?X6 and with tolerance factor value t < 1 crystallize in the elpasolite (ordered perovskite) structure. Different preparative methods have been considered. For example, the Bridgman technique is the most suitable method of growing single crystals of halogenated elpasolites with monoatomic cations. Group-theory and symmetry analyses have allowed us to build a scheme of possible structural distortions connected with octahedral rotations and displacements of ions. Experimental observations have proven that ferroelastic phase transitions occurring most frequently in elpasolites are due to small octahedra tilts. Quantitative analysis allows the possibility of describing these transitions in the framework of the thermodynamic Landau theory. Hydrostatic pressure and the substitution of atoms in different crystallographic sites allow to change significantly the succession and the temperature of phase transitions. The hypothesis of bond stresses is able to predict the possible occurrence of a phase transition for a particular elpasolite and/or the role of the octahedra rotations in the transformation. The mechanism of phase transitions in elpasolites and related compounds has also been considered. One can assume that a displacive mechanism associated with a strong anharmonicity plays a large role in phase transitions occurring in compounds with monoatomic cations. On the other hand, for instance, in cryolites with ammonium cations, the transitions originate from an order-disorder phenomenon. В© 1998 Elsevier Science S.A. All rights reserved.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Aleksandrov K. S., Tressaud A., Zaitsev A. I., Ushakova T. V., Durand E.
Заглавие : Phase transitions and pressure-temperature phase diagrams of ammonium containing cryolites and elpasolites
Коллективы : International Meeting on Ferroelectricity (10; 2001 ; 3-7 Sept.; Madrid)
Место публикации : Abstracts of the 10-th International Meeting on Ferroelectricity (IMF-10). - 2001. - P.153
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GOREV M. V., FLEROV I. N., VORONOV V. N., MISYUL S. V.
Заглавие : P = T-PHASE DIAGRAMS OF ELPASOLITES RB2KB3+F6(B3+ = HO,DY,TB)
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1993. - Vol. 35, Is. 4. - P1022-1027. - ISSN 0367-3294
Примечания : Cited References: 16
Предметные рубрики: RIGID SPHERE MODEL
RB2KMIIIF6 ELPASOLITES
TRANSITIONS
ORDER
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19.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vtyurin A.N., Krylov A.S., Gerasimova Ju.V., Ivanenko A.A., Shestakov N.P., Laptash N.M.
Заглавие : Ordering processes and phase transitions in ammonium-containing crystals of A2BWO3F3 elpasolites – com?parative Raman and infrared study
Коллективы : International Seminar on Ferroelastic Physics
Место публикации : The 6th International Seminar on Ferroelastics Physics (ISFP-6): Voronezh, September 22–25, 2009. - С. 23
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vtyurin A.N., Krylov A.S., Gerasimova Ju.V., Ivanenko A.A., Shestakov N.P., Laptash N.M.
Заглавие : Ordering processes and phase transitions in ammonium-containing crystals of A2BWO3F3 elpasolites – com?parative Raman and infrared study
Коллективы : IEEE International Symposium on Applications of Ferroelectrics, International Meeting on Ferroelectricity
Место публикации : The 12th International Meeting on Ferroelectricity and 18th IEEE International Symposium on Applications of Ferroelectrics (IMF-ISAF 2009): Xi'an, China, August 23-27, 2009 . - 2009. - Ст.OA-040
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