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Найдено документов в текущей БД: 35

    Lattice dynamics and phase transitions in A[[d]]2[[/d]]BMeF[[d]]6[[/d]] elpasolites studied by raman scattering
/ A. S. Krylov [и др.] // Proc. Joint Int. Symp: 11th Int. Symp. on Ferroic Domains and Micro-to Nanoscopic Structures and 11th - Russia/CIS/Baltic/Japan Symp. on Ferroelectricity. - 2012. - P207



Доп.точки доступа:
Vtyurin, A. N.; Втюрин, Александр Николаевич; Oreshonkov, A. S.; Орешонков, Александр Сергеевич; Krylov, A. S.; Крылов, Александр Сергеевич; Krylova, S. N.; Крылова, Светлана Николаевна; Goryainov, S. V.; Горяйнов, Сергей Владимирович; Voronov, V. N.; Воронов, Владимир Николаевич; Объединенный международный симпозиум ISFD-11th-RCBJSF (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); International Symposium on Ferroic Domains and Micro- to Nanoscopic Structures (11 ; 2012 ; Aug. ; 20-24 ; Ekaterinburg); Международный симпозиум по доменам в ферроиках, микро- и нано-масштабным структурам (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); Russian-CIS-Baltic-Japan Symposium on Ferroelectricity (11 ; 2012 ; Aug. ; 20-24 ; Ekaterinburg); Российско-Японский и стран Балтии и СНГ симпозиум по сегнетоэлектричеству (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); Уральский Федеральный университет им. Первого Президента России Б.Н. Ельцина

    Lattice dynamics and phase transitions in A2BMeF6 elpasolites studied by raman scattering
/ A. N. Vtyurin [et al.] // Proc. Joint Int. Symp: 11th Int. Symp. on Ferroic Domains and Micro-to Nanoscopic Structures and 11th - Russia/CIS/Baltic/Japan Symp. on Ferroelectricity. - 2012. - P. 55



Доп.точки доступа:
Vtyurin, A. N.; Втюрин, Александр Николаевич; Goryainov, S. V.; Krylov, A. S.; Крылов, Александр Сергеевич; Krylova, S. N.; Крылова, Светлана Николаевна; Oreshonkov, A. S.; Орешонков, Александр Сергеевич; Voronov, V. N.; Воронов, Владимир Николаевич; Объединенный международный симпозиум ISFD-11th-RCBJSF (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); International Symposium on Ferroic Domains and Micro- to Nanoscopic Structures (11 ; 2012 ; Aug. ; 20-24 ; Ekaterinburg); Международный симпозиум по доменам в ферроиках, микро- и нано-масштабным структурам (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); Russian-CIS-Baltic-Japan Symposium on Ferroelectricity (11 ; 2012 ; Aug. ; 20-24 ; Ekaterinburg); Российско-Японский и стран Балтии и СНГ симпозиум по сегнетоэлектричеству (11 ; 2012 ; авг. ; 20-24 ; Екатеринбург); Уральский Федеральный университет им. Первого Президента России Б.Н. Ельцина

    Heat capacity and structure of Rb2KMeO3F3 (Me: Mo, W) elpasolites
/ A. V. Kartashev [et al.] // Solid State Sci. - 2012. - Vol. 14, Is. 1. - P. 166-170, DOI 10.1016/j.solidstatesciences.2011.11.019. - Cited References: 12. - This study was supported by the Siberian Branch of the Russian Academy of Sciences (Grant no. 34) and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (NSh-4645.2010.2). . - ISSN 1293-2558
РУБ Chemistry + Physics
Рубрики:
T PHASE-DIAGRAM
   Rb2KMoO3F3

   TRANSITION

Кл.слова (ненормированные):
Oxyfluorides -- Crystal structure -- Phase transition -- Calorimetry

Аннотация: X-ray and heat capacity measurements were performed on Rb2KMoO3F3 and Rb2KWO3F3 single crystals. A significant difference in the thermal parameters of atoms in 4a and 8c sites of Fm-3m structure was found, which depended on the central atom. Calorimetric measurements have revealed the heat capacity anomalies at 195 and 67 K, respectively, in Rb2KMoO3F3 and Rb2KWO3F3. The standard molar enthalpy and entropy were determined. Entropy changes associated with phase transitions in oxyfluorides under study and related Rb2KTiOF5 are discussed. 2011 Elsevier Masson SAS. All rights reserved.

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Держатели документа:
[Gorev, Michail V.] Russian Acad Sci, Siberian Div, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
[Kartashev, Andrey V.
Gorev, Michail V.
Flerov, Igor N.] Siberian Fed Univ, Inst Engn Phys & Radio Elect, Krasnoyarsk 660074, Russia
[Isaenko, Lyudmila I.
Zhurkov, Sergey A.] Russian Acad Sci, Inst Geol & Mineral, Novosibirsk 630090, Russia

Доп.точки доступа:
Kartashev, A. V.; Карташев, Андрей Васильевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Isaenko, L. I.; Zhurkov, S. A.; Fokina, V. D.; Фокина, Валентина Дмитриевна; Gorev, M. V.; Горев, Михаил Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич; Siberian Branch of the Russian Academy of Sciences [34]; Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-4645.2010.2]

    A raman study of hydrostatic pressure induced phase transitions in Rb2KInF6 crystals
/ A. N. Vtyurin [et al.] // Phys. Solid State. - 2012. - Vol. 54, Is. 5. - P. 934-936, DOI 10.1134/S1063783412050472. - Cited References: 16. - This study was supported by the Russian Foundation for Basic Research (project nos. 11-02-98002-r_sibir' and 09-02-00062), the Siberian Branch of the Russian Academy of Sciences (integration project no. 101), and the Council on Grants from the President of the Russian Federation (grant no. HSh-4645.2010.2). . - ISSN 1063-7834
РУБ Physics, Condensed Matter

Аннотация: The Raman spectra of the elpasolite (Rb2KInF6) crystal have been studied in the pressure range from 0 to 5.3 GPa at a temperature of 295 K. A phase transition at a pressure of approximately 0.9 GPa has been found. An analysis of the variations in the spectral parameters has led to the conclusion that the phase transition to a distorted phase is accompanied by the doubling of the volume of the primitive cell of the initial cubic phase. Numerical calculations of the lattice dynamics in the Rb2KInF6 crystal have been performed. The numerical simulation has established that the phase transition at a pressure of 0.9 GPa is associated with condensation of the F (lg) mode. A probable high-pressure phase is the phase with space group C2/m.

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Держатели документа:
[Vtyurin, A. N.
Krylov, A. S.
Krylova, S. N.
Oreshonkov, A. S.
Voronov, V. N.] Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
[Goryainov, S. V.] Russian Acad Sci, Siberian Branch, Inst Mineral & Petrog, Novosibirsk 630090, Russia

Доп.точки доступа:
Vtyurin, A. N.; Втюрин, Александр Николаевич; Krylov, A. S.; Крылов, Александр Сергеевич; Goryainov, S. V.; Горяйнов, Сергей Владимирович; Krylova, S. N.; Крылова, Светлана Николаевна; Oreshonkov, A. S.; Орешонков, Александр Сергеевич; Voronov, V. N.; Воронов, Владимир Николаевич

    Raman spectra and ordering processes in alcaline-tungsten oxyfluorides
/ K. S. Aleksandrov [et al.] // Ferroelectrics. - 2007. - Vol. 347. - P. 79-85, DOI 10.1080/00150190601187070. - Cited References: 8 . - ISSN 0015-0193
РУБ Materials Science, Multidisciplinary + Physics, Condensed Matter

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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Доп.точки доступа:
Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Vtyurin, A. N.; Втюрин, Александр Николаевич; Gerasimova, J. V.; Герасимова, Юлия Валентиновна; Krylov, A. S.; Крылов, Александр Сергеевич; Laptash, N. M.; Voyt, E. I.; Kocharova, A. G.; Кочарова, Алла Георгиевна; Surovtsev, S. V.; Russian-CIS-Baltic-Japanese symposium on ferroelectricity(8 ; 2006 ; May ; 15-19 ; Tsukuba, Japan)

    Ferroelastic phase transitions in fluorides with cryolite and elpasolite structures
/ I. N. Flerov [et al.] // Crystallogr. Rep. - 2004. - Vol. 49, Is. 1. - P. 100-107, DOI 10.1134/1.1643969. - Cited References: 43 . - ISSN 1063-7745
Аннотация: The ferroelastic phase transitions are investigated in several series of fluoride crystals belonging to the elpasolite and cryolite families (space group Fm (3) over barm) with the general formula A(2)BB'F-6. The influence of the size and shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2004 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Kirensky Inst Phys, Siberian Div, Krasnoyarsk 660036, Russia
Inst Chim Mat Condensee Bordeaux, F-33608 Pessac, France
ИФ СО РАН

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Tressaud, A.; Fokina, V. D.; Фокина, Валентина Дмитриевна

    Structural distortions in families of perovskite-like crystals
/ K. S. Aleksandrov, J. . Bartolome // Phase Transit. - 2001. - Vol. 74, Is. 3. - P. 255-335, DOI 10.1080/01411590108228754. - Cited References: 262 . - ISSN 0141-1594
РУБ Crystallography + Physics, Condensed Matter

Аннотация: The crystallographic and group theoretical analysis of the structural phase transitions in perovskite and perovskite-like crystals is reviewed. We include ABX(3) perovskites and their relative crystals of ReO3 type (G(0) = O-h(1)), elpasolites, cryolites and their relatives (G(0) = O-h(5)) layered crystals of TIAIF(4) series (G(0) = D-4h(1)), Aurivillius and Ruddlesden-Popper series (G(0) = D-4h(17)). The structures in their initial phase G(0) often contain n layers (n = 1, 2,3) of vertex linked octahedra. The distorted phases produced by one kind of tilt and by superposition of tilts in the slabs are enumerated. Most of the tilts correspond to symmetry changes, which can be associated to definite librational lattice modes irreducible representations of the G(0) group. The softening of modes associated to the PT has been found experimentally in many perovskites, elpasolites and layered crystals with n = 1. In contrast, no such soft modes have been found yet for even-layered (n = 2) crystals. Examples of successive phase transitions due to the superposition of tilts in these types of crystals have been collected.

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Держатели документа:
LV Kirenskii Inst Phys, Siberian Branch, Russian Acad Sci, Krasnoyarsk 660036, Russia
Univ Zaragoza, CSIC, Inst Ciencias Mat Aragon, Zaragoza, Spain
ИФ СО РАН

Доп.точки доступа:
Bartolome, J.; Александров, Кирилл Сергеевич

    Study of the Fm3m-]14/m-]P21/n successive phase-transitions in Rb2KINF6 and Rb2KLUF6 elpasolites
/ I. N. Flerov [et al.] // Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 11. - P. 3493-3500. - Cited References: 13 . - ISSN 0367-3294

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Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Melnikova, S. V.; Мельникова, Светлана Владимировна; Misyul, S. V.; Мисюль, Сергей Валентинович; Voronov, V. N.; Воронов, Владимир Николаевич; Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Tressaud, A.; Grannec, J.; Shaminade, J. P.; Rabardel, L.; Guingard, H.

    Phase-transitions in elpasolite Rb2KSCF6
/ I. N. Flerov [et al.] // Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 7. - P. 2185-2195. - Cited References: 24 . - ISSN 0367-3294

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Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Melnikova, S. V.; Мельникова, Светлана Владимировна; Misyul, S. V.; Мисюль, Сергей Валентинович; Voronov, V. N.; Воронов, Владимир Николаевич; Aleksandrov, K. S.; Александров, Кирилл Сергеевич

    Symmetrical analysis of structural phase transitions in crystals with the Oh 5 space group
/ K. S. Aleksandrov, S. V. Misyul, E. E. Baturinets // Ferroelectrics. - 2007. - Vol. 354, Is. 1. - P. 60-68, DOI 10.1080/00150190701454529. - Cited References: 13 . - ISSN 0015-0193
Аннотация: Using the group-theoretical methods, the complete set of critical and noncritical order parameters arising at phase transitions in crystals with the Oh 5- Fm3m space group has been obtained and analyzed. The mechanical and permutation representations have been constructed, and their composition for all the right systems of points of the Oh 5 space group has been determined. Experimental data on structural phase transitions in ammonium cryolites and elpasolites have been considered.

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Держатели документа:
Siberian Federal University, 660041 Krasnoyarsk, Russian Federation
L. V. Kirensky Institute of Physics, 660036 Krasnoyarsk, Russian Federation
Scientific and Research Institute of Physics, Southern Federal University, 344090 Rostov-on-Don, Russian Federation

Доп.точки доступа:
Misyul, S. V.; Мисюль, Сергей Валентинович; Baturinets, E. E.; Александров, Кирилл Сергеевич

    Phase transitions in elpasolites (ordered perovskites)
/ I. N. Flerov [et al.] // Materials Science and Engineering R: Reports. - 1998. - Vol. 24, Is. 3. - P. 81-151. - Cited References: 174 . - ISSN 0927-796X
РУБ Materials Science, Multidisciplinary + Physics, Applied

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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Держатели документа:
L.V. Kirensky Institute of Physics, Krasnoyarsk 660036, Russian Federation
Inst. Chim. Matiere Cond. B., Universite Bordeaux I, 33608, Pessac Cedex, France
Lab. de Phys.-Chim. Molec., Universite Bordeaux I, 33405, Talence Cedex, France

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Tressaud, A.; Grannec, J.; Couzi, M.

    Structural transformations and phenomenological description of the formation of phase states in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb)
/ I. N. Safonov [et al.] // Phys. Solid State. - 2015. - Vol. 57, Is. 3. - P. 491-498, DOI 10.1134/S1063783415030282. - 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). . - ISSN 1063. - ISSN 1090-6460. -
РУБ Physics, Condensed Matter
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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Держатели документа:
Siberian Fed Univ, Krasnoyarsk 660041, Russia.
Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia.
Southern Fed Univ, Inst Phys Res, Rostov Na Donu 344090, Russia.

Доп.точки доступа:
Safonov, I. N.; Misyul', S. V.; Мисюль, Сергей Валентинович; Molokeev, M. S.; Молокеев, Максим Сергеевич; Ivliev, M. P.; Ministry of Education and Science of the Russian Federation [3.2534.2014/K]

    Phase transitions and pressure-temperature phase diagrams of ammonium containing cryolites and elpasolites
/ M. V. Gorev [и др.] // Abstracts of the 10-th International Meeting on Ferroelectricity (IMF-10). - 2001. - P. 153



Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич; Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Tressaud, A.; Zaitsev, A. I.; Зайцев, Александр Иванович; Ushakova, T. V.; Durand, E.; International Meeting on Ferroelectricity (10 ; 2001 ; 3-7 Sept. ; Madrid)

    Effect of B3+ ion size on the phase transitions in Rb2KB3+F6 elpasolites series
/ I. N. Flerov [et al.] // Ferroelectrics. - 1991. - Vol. 124, Is. 1. - P. 309-314, DOI 10.1080/00150199108209457 . - ISSN 0015-0193

Аннотация: The physical properties of Rb2KScF6 crystal characterized by the medium size of B3+ atom in Rb2KB3+F6 series are studied. The two successive phase transitions from cubic into tetragonal and then into monoclinic phases are found. The results are discussed in view of the influence of B3+ atom size on structural transformations.

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Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Tressaud, A.; Aleksandrov, K. S.; Александров, Кирилл Сергеевич; Couzi, M.; Gorev, M. V.; Горев, Михаил Васильевич; Grannec, J.; Melnikova, S. V.; Мельникова, Светлана Владимировна; Chaminade, J. P.; Misul, S. V.; Мисюль, Сергей Валентинович; Voronov, V. N.; Воронов, Владимир Николаевич

    Entropy and the mechanism of phase transitions in elpasolites
/ I. N. Flerov, M. V. Gorev // Phys. Solid State. - 2001. - Vol. 43, Is. 1. - P. 127-136, DOI 10.1134/1.1340198. - Cited References: 33 . - ISSN 1063-7834
РУБ Physics, Condensed Matter

Аннотация: The phase transitions in series of crystals with the general formulas A(2)BB'X-6 (X = F, Cl, Br, or CN) and Pb2BB'O-6 that belong to the elpasolite family (space group Fm(3) over bar m) are analyzed. The influence of the size and the shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2001 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirenskii Inst. of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Флёров, Игорь Николаевич

    Lattice dynamics and statistical mechanics of the Fm3m - I4/m structural phase transition in Rb2KInF6
/ V. I. Zinenko, N. G. Zamkova // Phys. Solid State. - 2001. - Vol. 43, Is. 12. - P. 2290-2300, DOI 10.1134/1.1427959. - Cited References: 18 . - ISSN 1063-7834
РУБ Physics, Condensed Matter

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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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Zamkova, N. G.; Замкова, Наталья Геннадьевна; Зиненко, Виктор Иванович

    Theory of an Fm3m - I4/m structural phase transition in an Rb2KScF6 crystal
/ V. I. Zinenko, N. G. Zamkova // J. Exp. Theor. Phys. - 2000. - Vol. 91, Is. 2. - P. 314-323, DOI 10.1134/1.1311990. - Cited References: 16 . - ISSN 1063-7761
РУБ Physics, Multidisciplinary

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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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН

Доп.точки доступа:
Zamkova, N. G.; Замкова, Наталья Геннадьевна; Зиненко, Виктор Иванович

    Calorimetric investigations of phase transitions in the cryolites (NH4)(3)Ga1-xScxF6 (x = 1.0, 0.1, 0)
/ I. N. Flerov, M. V. Gorev, T. V. Ushakova // Phys. Solid State. - 1999. - Vol. 41, Is. 3. - P. 468-473, DOI 10.1134/1.1130805. - Cited References: 19 . - ISSN 1063-7834
РУБ Physics, Condensed Matter

Аннотация: The specific heat of the cryolites (NH4)(3)Ga1-xScxF6 with x=1.0, 0.1, and 0 was measured. The thermodynamic parameters of the phase transitions were determined. A previously unknown phase transition was found in the scandium compound at T=243 K. (C) 1999 American Institute of Physics. [S1063-7834(99)03003-8].

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
ИФ СО РАН

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Ushakova, T. V.; Флёров, Игорь Николаевич

    THERMODYNAMIC PROPERTIES OF ELPASOLITES CS2NANDCL6 AND CS2NAPRCL6
/ M. V. GOREV [et al.] // JOURNAL OF PHYSICS C-SOLID STATE PHYSICS. - 1986. - Vol. 19, Is. 14. - P. 2441-2447, DOI 10.1088/0022-3719/19/14/010. - Cited References: 20 . - ISSN 0022-3719
РУБ Physics, Condensed Matter


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Держатели документа:
L v Kirensky Institute of Physics, Academy of Sciences of the USSR, Siberian Branch, 660036 Krasnoyarsk, Russian Federation
Доп.точки доступа:
GOREV, M. V.; Горев, Михаил Васильевич; MISYUL, S. V.; Мисюль, Сергей Валентинович; BOVINA, A. F.; Бовина, Ася Федоровна; ISKORNEV, I. M.; KOKOV, I. T.; FLEROV, I. N.; Флёров, Игорь Николаевич

    T-x phase diagram of mixed elpasolites Rb2KGaxSc1-xF6
/ M. V. Gorev [и др.] // Izv. Akad. Nauk Ser. Fiz. - 1998. - Vol. 62, Is. 8. - P. 1532-1536. - Cited References: 12 . - ISSN 1026-3489
РУБ Physics, Multidisciplinary


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Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич; Bovina, A. F.; Бовина, Ася Федоровна; Chernenko, T. V.; Tressand, A.; Grannes, J.; International Seminar on Physics of Ferroelastics(2 ; 1997 ; Jun 25-27 ; Kazan, Russia)