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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Incommensurate magnetic structures in rhombohedral Heisenberg antiferromagnet
Место публикации : JETP Letters. - 2013. - Vol. 98, Is. 1. - P.19-23. - 5. - ISSN 0021-3640, DOI 10.1134/S0021364013140099
Примечания : Cited References: 31
Предметные рубрики: DISORDER
Аннотация: The phase diagram of the ground state has been calculated for a rhombohedral antiferromagnet of the R3m symmetry with frustrated exchange in the base plane and competition of exchanges between the nearest and next-nearest planes. The diagram contains phases of collinear antiferromagnetic ordering of various types separated by five incommensurate magnetic states of the helicoidal type, differing in the ordering type and in the direction of the modulation vector. The commensurate and incommensurate phases converge at multi-critical points lying on a line corresponding to an antiferromagnet with an undistorted simple cubic lattice.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Merkushova E. M., Vtyurin A. N., Isaenko L. I.
Заглавие : Raman spectroscopic study of the lattice dynamics in the Rb2KMoO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 6. - P.1275-1280. - ISSN 1063-7834, DOI 10.1134/S1063783412060170
Примечания : Cited References: 24. - This study was supported by the Russian Foundation for Basic Research (project nos. 11-02-98002-r_sibir', 09-02-00062, and NSh-4645.2010.2).
Предметные рубрики: PHASE-TRANSITIONS
SCATTERING
(NH4)3WO3F3
CRYSTALS
DISORDER
Cs
Аннотация: The lattice dynamics of the Rb2KMoO3F3 oxyfluoride has been studied by Raman spectroscopy in the temperature range 7–400 K. A phase transition has been revealed at T ≈ 185 K with decreasing temperature. Anomalies of the frequencies and Raman line half-widths have been analyzed. No condensation of soft lattice modes has been found. The character of changes in the Raman spectra of the Rb2KMoO3F3 oxyfluoride shows that the phase transition is related to variations in the [MoO3F3]3− molecular octahedron.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Sofronova S. N., Kolesnikova E. M., Vtyurin A. N., Isaenko L. I.
Заглавие : Lattice dynamics of oxyfluoride Rb2KMoO3F3
Коллективы : International Symposium on Ferroic Domains and Micro- to Nanoscopic Structures, Russia/CIS/Baltic/Japan Symposium on Ferroelectricity
Место публикации : Ferroelectrics: Taylor & Francis LTD, 2012. - Vol. 441. - P.52-60. - ISSN 0015-0193, DOI 10.1080/00150193.2012.743791
Примечания : Cited References: 23
Предметные рубрики: PHASE-TRANSITIONS
RAMAN-SCATTERING
ELPASOLITE
CRYSTALS
DISORDER
SPECTRA
CS
Ключевые слова (''Своб.индексиров.''): oxyfluorides--lattice dynamics--ramam measurements
Аннотация: The complete Raman spectra of oxyfluoride Rb2KMoO 3F3 were obtained. At T ≈ 185 K phase transitions were found. Lattice dynamics of disordered structures of the investigated compound was simulated, and "soft" vibrational modes were found in the calculated spectrum. Copyright © Taylor & Francis Group, LLC.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Goryainov S. V., Laptash N. M., Vtyurin A. N., Mel'nikova S. V., Krylova S. N.
Заглавие : Influence of the molecular groups ordering on structural phase transitions in (NH4)2WO2F4 crystal
Место публикации : Cryst. Growth Des.: American Chemical Society, 2014. - Vol. 14, Is. 1. - P.374-380. - ISSN 1528-7483, DOI 10.1021/cg400899m. - ISSN 1528-7505
Примечания : Cited References: 27. - This work was partly supported by the Russian Foundation for the Basic Research project no. 12-02-00056, no. 13-02-00825, and integration project SB RAS no. 28, SS-4828.2012.2.Published as part of the Crystal Growth & Design virtual special issue Anion-controlled New Inorganic Materials.
Предметные рубрики: RAMAN-SCATTERING
NEUTRON-SCATTERING
SOLID-STATE
OXYFLUORIDES
DISORDER
POLAR
ANION
Аннотация: Phase transitions of the (NH4)2WO2F 4 crystal were studied by Raman spectroscopy in the range from 10 to 350 K. The mechanism of two phase transitions at T1 = 201 and T 2 = 160 K was proposed. The significant spectra changes occur in the range corresponding to the W-O vibrations. The first temperature phase transition is due to the ordering of the quasi-octahedral groups [WO 2F4]2- and partial ordering of ammonium groups. Experimental data allow for attributing the first (T1 = 201 K) phase transition to the first order close to the tricritical point. The noticeable changes of the Raman spectrum have been found in the range corresponding to the ammonium vibrations below the temperature T2. The second phase transition is associated with the further ordering of ammonium groups. Room temperature (296 K) experiments have been carried out under high hydrostatic pressure up to 10 GPa. Above 2 GPa, new spectral features appear, allowing for the assumption of the existence of a new high-pressure phase of (NH 4)2WO2F4, which is mainly connected with ordering of the [WO2F4]2- quasi-octahedral groups.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Laptash N. M., Vtyurin A. N.
Заглавие : Raman scattering study of temperature induced phase transitions in crystalline ammonium heptafluorozirconate, (NH4)3ZrF7
Место публикации : Vib. Spectrosc.: Elsevier Science BV, 2012. - Vol. 62. - P.258-263. - ISSN 0924-2031, DOI 10.1016/j.vibspec.2012.07.003
Примечания : Cited References: 31. - This work was partly supported by integration project SB RAS No 28, Russian Foundation for Basic Research project No 11-02-98002-r_siberia, No 12-02-00056, SS-4828.2012.2. The authors are grateful to Dr. I.N. Flerov for helpful discussions. The assistance of Dr. S. Skokov is sincerely appreciated.
Предметные рубрики: VIBRATIONAL-SPECTRA
X-RAY
DISORDER
DIFFRACTION
ELPASOLITE
SYMMETRY
RB2KSCF6
IF7
Ключевые слова (''Своб.индексиров.''): raman spectroscopy--phase transition--ammonium heptafluorozirconate--low temperature
Аннотация: This paper reports on a Raman spectroscopy investigation of phase transitions in (NH4)3ZrF7 crystal. Raman spectra were obtained and analyzed in a wavenumber range from 3800 to 15 cm−1 and in the temperature range from 7 to 360 K. The anomalies caused by a series of subsequent structural phase transitions have been analyzed. A soft phonon mode restoring in the distorted phase was found. The spectral changes observed in the current study are similar to those typically found in phase transitions near a tricritical point. The spectral changes in the middle wavenumber range, 700–150 cm−1, indicate that the phase transitions are due to structural ordering of pentagonal ZrF73− bipyramids. Spectral data also show that a phase transition near 225 K is accompanied by an increase of the unit cell volume. In addition, spectral changes in the range of internal vibrations of ammonium ions indicate that the ion's motion slows down with decrease of temperature.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Molokeev M. S., Misyul' S. V.
Заглавие : Processes of ordering of structural elements, critical and noncritical parameters of phase transitions in the (NH4)3WO3F3 crystal
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 1. - P.155-165. - ISSN 1063-7834, DOI 10.1134/S1063783412010222. - ISSN 1090-6460
Примечания : Cited References: 18. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-4645.2010.2).
Предметные рубрики: OXYFLUORIDE
TRANSFORMATIONS
(NH4)3TiOF5
DISORDER
Аннотация: The structure of the low-temperature triclinic phase of the (NH4)3WO3F3 crystal has been determined and the structure of the cubic phase of this crystal has been refined from data of an X-ray diffraction experiment performed for a powder sample. The profile and structural parameters have been refined according to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic orderings and allows one to interpret the obtained experimental data. It has been found that the symmetry transformation in the crystal can be schematically represented in the following form: Fm3¯m(Z=4)→P1¯(Z=1)→P1¯(Z=6)Fm\bar 3m(Z = 4) \to P\bar 1(Z = 1) \to P\bar 1(Z = 6) . This transformation is accompanied by the complete ordering of WO3F3 polyhedra and the displacement of NH4 ions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Solovyov L. A., Fedorov A. S., Kuzubov A. A.
Заглавие : Complete crystal structure of decafluorocyclohex-1-ene at 4.2 K from original neutron diffraction data
Место публикации : Acta Crystallogr. B: Wiley-Blackwell, 2014. - Vol. 70. - P.395-397. - ISSN 0108-7681, DOI 10.1107/S2052520613031028. - ISSN 1600-5740
Примечания : Cited References: 20
Предметные рубрики: AUGMENTED-WAVE METHOD
POWDER DIFFRACTION
NORMAL-BUTANE
REFINEMENT
DISORDER
Аннотация: The crystal structure model of decafluorocyclohex-1-ene at 4.2 K derived from simulated powder diffraction data and solid-state energy minimization [Smrcok et al. (2013). Acta Cryst. B69, 395-404] is found to be incomplete. In this study it is completed by an additional alternative molecular orientation revealed from the difference density analysis and direct space search. The structure is refined by the derivative difference method in the rigid-body approximation leading to perfect agreement between observed and calculated neutron powder patterns.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Molokeev M. S., Misjul S. V., Flerov I. N., Laptash N. M.
Заглавие : Reconstructive phase transition in (NH4)3TiF7 accompanied by the ordering of TiF6 octahedra
Место публикации : Acta Crystallogr. B: Wiley-Blackwell, 2014. - Vol. 70. - P.924-931. - ISSN 0108-7681, DOI 10.1107/S2052520614021192. - ISSN 1600-5740
Примечания : This study was supported by Russian Fund of Basic Research, project No. 12-02-00056 a
Предметные рубрики: CRYSTAL-STRUCTURE
NEUTRON-DIFFRACTION
POWDER DIFFRACTION
FLUORIDES
DISORDER
MECHANISM
PATHWAYS
COMPLEX
LI3THF7
ALPHA
Ключевые слова (''Своб.индексиров.''): reconstructive phase transition--ammonium heptafluorotitanate--order-disorder transition
Аннотация: An unusual phase transition P4/mnc →Pa3 has been detected after cooling the (NH4)3TiF7 compound. Some TiF6 octahedra, which are disordered in the room-temperature tetragonal structure, become ordered in the low-temperature cubic phase due to the disappearance of the fourfold axis. Other TiF6 octahedra undergo large rotations resulting in huge displacements of the F atoms by 1.5-1.8 Å that implies a reconstructive phase transition. It was supposed that phases P4/mbm and Pm3m could be a high-temperature phase and a parent phase, respectively, in (NH4)3TiF7. Therefore, the sequence of phase transitions can be written as Pm3m → P4/bm → P4/mnc → Pa3. The interrelation between (NH4)3TiF7, (NH4)3GeF7 and (NH4)3PbF7 is found, which allows us to suppose phase transitions in relative compounds.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S.
Заглавие : Phase-transitions and distortions of the structure in the family of crystals related to alpha-k2so
Место публикации : Kristallografiya. - 1993. - Vol. 38, Is. 1. - P.128-139. - ISSN 0023-4761; Crystallogr. Rep.
Примечания : Cited References: 38
Предметные рубрики: X-RAY
EXPECTED STRUCTURES
A2BX4 COMPOUNDS
TEMPERATURE
(NH4)2BEF4
CHEMISTRY
DISORDER
SYMMETRY
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M.
Заглавие : Optical studies of the (T-x) phase diagram of oxyfluoride (NH4)2MoO2F4-Rb2MoO2F4 solid solutions
Коллективы : Russian Federation [NSh-924.2014.2]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 6. - P.1201-1205. - ISSN 1063, DOI 10.1134/S1063783415060256. - ISSN 10906460(eISSN)
Примечания : Cited References:8. - This study was supported by the Council on Grants from the President of the Russian Federation for Supporting of Leading Scientific Schools of the Russian Federation (grant NSh-924.2014.2).
Предметные рубрики: TRANSITIONS
(NH4)2WO2F4
CRYSTALS
DISORDER
Аннотация: Single crystals of solid solutions (NH4)2 − x Rb x MoO2F4 (including individual complex Rb2MoO2F4) have been grown and studied using polarization-optical methods. The birefringence Δn(T) has been measured in the temperature range of 100–400 K. The complete (T-x) phase diagram has been constructed.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Vasilev A. D., Kocharova A. G.
Заглавие : The role of structural and nonstructural water in oxyfluoride K2WO2F4 center dot H2O
Разночтения заглавия :авие SCOPUS: The role of structural and nonstructural water in oxyfluoride K2WO2F4 В· H2O
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 12. - P2435-2440. - ISSN 1063-7834, DOI 10.1134/S1063783411120146
Примечания : Cited References: 16. - This work was supported by the Presidential Grant of the Russian Federation NSh-4645.2010.2, by the Russian Foundation for Basic Research, project no. 09-02-00062, and by the Integration Project of the Siberian Branch of the Russian Academy of Sciences no. 101.
Предметные рубрики: PHASE-TRANSITIONS
OXOPEROXOFLUORO COMPLEXES
MO V
CRYSTAL STRUCTURE
OXOFLUORO
(NH4)(2)NBOF5
(NH4)(2)WO2F4
MONOHYDRATE
DISORDER
Аннотация: X-ray structural and polarization optical investigations have been performed, and birefringence and rotation angles of the optical indicatrix phi (b) and phi (c) of the K2WO2F4 center dot H2O crystal have been measured in the temperature range of 100-600 K. The structure and symmetry of compounds at room temperature have been refined. It has been established that the layered crystal K2WO2F4 center dot H2O can exist in two states (A and B) depending on the atmospheric humidity and undergoes the sequence of reversible and irreversible phase transformations G (3)↔ G (2)↣ G (1)↣ G (0). The sequences of changes in the phase symmetry P (1) over bar↔C2/m↣ {4/nmm for samples A and m↔ C2/m↣P4/nmm for samples B havve been found. The second older proper ferroelastic phase transition (P(1) over bar↔ C2/m) at T-03 = 2700-290 K (G (3)↔ G (2)) is accompanied by twinning and appearance of the shift deformation x (6). The crystal system of the substance for the B crystals remains invariable after the second-order phase transition G (3) a dagger" G (2). The irreversible first-order phase transition G (2)↣ G (1) occurs in a temperature range T (02) a parts per thousand 350-380 K; it is accompanied by the loss of the crystallization water, which then is reduced easily from the atmosphere for a day. The substance decomposes at T (01) approximate to 510 K (G (1)↣ G (0)). The distinction between the A and B crystals has been explained by the presence or absence of free water in interlayer spacings.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Bovina A. F., Bogdanov E. V., Pogorel'tsev E. I., Laptash N. M., Gorev M. V., Flerov I. N.
Заглавие : Specific heat, cell parameters, phase T-p diagram, and permittivity of cryolite (NH4)(3)Nb(O-2)(2)F-4
Разночтения заглавия :авие SCOPUS: Specific heat, cell parameters, phase T-p diagram, and permittivity of cryolite (NH4)3Nb(O2)2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 10. - P2147-2153. - ISSN 1063-7834, DOI 10.1134/S1063783411100131
Примечания : Cited References: 19. - This study was performed within the Interdisciplinary integration project of the Siberian Branch of the Russian Academy of Science no. 34 and supported by the grant of the President of the Russian Federation for Leading Scientific Schools of the Russian Federation (NSh-4645.2010.2).
Предметные рубрики: CRYSTAL-STRUCTURES
TRANSITIONS
(NH4)(3)TIOF5
OXYFLUORIDE
COMPLEXES
CAPACITY
DISORDER
Аннотация: The temperature dependences of the specific heat, unit cell parameters, susceptibility to hydrostatic pressure, and permittivity of cryolite (NH4)(3)Nb(O-2)(2)F-4 have been studied. Phase transitions of nonferroelectric nature have been detected. Entropy parameters point to the relation of structure distortions to ordering processes.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Molokeev M. S., Misyul' S. V.
Заглавие : Structural transformations and the critical and noncritical parameters during the phase transition in the (NH4)(2)KWO3F3 oxyfluoride
Разночтения заглавия :авие SCOPUS: Structural transformations and the critical and noncritical parameters during the phase transition in the (NH4)2KWO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 8. - P1672-1679. - ISSN 1063-7834, DOI 10.1134/S1063783411080208
Примечания : Cited References: 18. - This study was supported by the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-4645.2010.2).
Предметные рубрики: MOLECULAR CRYSTALS
DISORDER
(NH4)(3)WO3F3
Аннотация: The structures of two phases of the (NH4)(2)KWO3F3 crystal have been determined from X-ray diffraction data obtained for a powder sample. The profile and structural parameters have been refined according to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic orderings and allows one to interpret the experimental data. It has been found that the symmetry transformation in the crystal can be schematically represented in the form Fm (3) over barm (10-10((X) over bar5)) - ((eta, 0, 0, 0, 0, 0)) Pmmn.This transformation is accompanied by the ordering of WO3F3 polyhedra and the displacement of NH4 and K ions.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogorel'tsev E. I., Bogdanov E. V., Molokeev M. S., Voronov V. N., Isaenko L. I., Zhurkov S. A., Laptash N. M., Gorev M. V., Flerov I. N.
Заглавие : Thermodynamic Properties and Structure of Oxyfluorides Rb(2)KMoO(3)F(3) and K(2)NaMoO(3)F(3)
Разночтения заглавия :авие SCOPUS: Thermodynamic properties and structure of oxyfluorides Rb2KMoO3F3 and K2NaMoO3F3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 6. - P1202-1211. - ISSN 1063-7834, DOI 10.1134/S1063783411060266
Примечания : Cited References: 24. - This study was supported by the Siberian Branch of the Russian Academy of Sciences within the framework of the Interdisciplinary Integration project no. 34 SO RAN and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-4645-2010.2).
Предметные рубрики: T PHASE-DIAGRAM
HEAT-CAPACITY
TRANSITIONS
(NH4)(3)MOO3F3
(NH4)(3)TIOF5
(NH4)(3)WO3F3
RB2KTIOF5
CRYSTALS
CRYOLITE
DISORDER
Аннотация: According to the results of calorimetric and structural studies, the Fm (3) over barm phase in K(2)NaMoO(3)F(3) remains stable at least to 100 K. No ferroelectric transformation assumed earlier has been revealed in a series of Rb(2)KMoO(3)F(3) samples prepared using various technologies. Only a phase transition of nonferroelectric origin has been observed near 195 K, and its thermodynamic characteristics have been determined. An analysis of the stability of the cubic structure of molybdenum fluorine-oxygen elpasolites-cryolites has been performed in the framework of the hypothesis on strengths of interatomic bonds. The barocaloric effect in Rb(2)KMoO(3)F(3) has been estimated.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bogdanov E. V., Vasil'ev A. D., Flerov I. N., Laptash N. M.
Заглавие : Effect of cation substitution in fluorine-oxygen molybdates (NH4)(2-x) A (x) MoO2F4
Разночтения заглавия :авие SCOPUS: Effect of cation substitution in fluorine-oxygen molybdates (NH4)2 - xAxMoO2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 2. - P303-308. - ISSN 1063-7834, DOI 10.1134/S1063783411020065
Примечания : Cited References: 11. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-1011.2008.2).
Предметные рубрики: PHASE-TRANSITIONS
CRYSTALS
(NH4)(2)WO2F4
DIFFRACTION
OXYFLUORIDE
MECHANISM
DISORDER
Аннотация: Thermophysical and structural studies of (NH4)(2 - x) A (x) MoO2F4 (A = Cs, Rb, K) solid solutions of oxyfluorides have been performed. The character of the influence of cation substitutions on the stability of the initial phase (space group Cmcm) and on the mechanism of phase transitions has been elucidated.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Bogdanov E. V., Gorev M. V., Molokeev M. S., Pogorel'tsev E. I., Flerov I. N., Laptash N. M.
Заглавие : Phase transitions in the (NH4)(2)NbOF5 oxyfluoride
Коллективы :
Разночтения заглавия :авие SCOPUS: Phase transitions in the (NH4)2NbOF5 oxyfluoride
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 4. - P781-788. - ISSN 1063-7834, DOI 10.1134/S1063783410040189
Примечания : Cited References: 13. - We would like to thank A. A. Udovenko (Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia) for kindly supplied detailed data on the atomic coordinates in the structure of the (NHINF4/INF)INF2/INFNbOFINF5/INF oxyfluoride.This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-1011.2008.2).
Предметные рубрики: CRYSTAL-STRUCTURE
(NH4)(2)WO2F4
MECHANISM
DISORDER
Аннотация: The thermal and dielectric properties of the (NH4)(2)NbOF5 oxyfluoride have been investigated. It has been established that the structural phase transitions Cmc2(1) - C2 - Ia observed at the temperatures T (1) = 258.0 K and T (2) = 218.9 K exhibit a nonferroelectric nature. The hydrostatic pressure, which stabilizes the initial phase and destabilizes the low-temperature phase, hardly affects the temperature range of stability of the intermediate phase. The model of sequential ordering of the structural elements due to phase transitions has been analyzed using experimental data on the entropies of the phase transitions.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics and the ferroelectric phase transition in ordered Pb-2 B'BaEuro(3)O(6) (B' = Ga, In, Lu; BaEuro(3) = Nb, Ta) solid solutions
Коллективы :
Разночтения заглавия :авие SCOPUS: Lattice dynamics and the ferroelectric phase transition in ordered Pb2 B′ B″O6 (B′ = Ga, In, Lu; B″ = Nb, Ta) solid solutions
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 2. - P357-363. - ISSN 1063-7834, DOI 10.1134/S1063783410020228
Примечания : Cited References: 19. - This study is supported by the Russian Foundation for Basic Research (project no. 09-02-00067) and the Council on Grants from the President of the Russian Federation for Support of the Leading Scientific Schools (grant no. NSh-4137.2006.2).
Предметные рубрики: PEROVSKITES
CRYSTALS
DISORDER
RELAXOR
BATIO3
PBTIO3
Аннотация: The lattice vibration spectrum, rf permittivity, and dynamic Born charges have been calculated for ordered Pb-2 B'BaEuro(3)O(3) (B'=Ga, In, Lu; BaEuro(3)=Nb, Ta) solid solutions in terms of the generalized Gordon-Kim model. It has been shown that all compounds exhibit a ferroelectric instability and that the frequencies of "soft" ferroelectric modes are close in magnitude. The ferroelectric phase-transition temperatures and the spontaneous polarization in the ferroelectric phase of the solid solutions under consideration have been calculated by the Monte Carlo method using the model Hamiltonian in the local mode approximation. The transition temperature is found to increase with increasing atomic number of the B' ion.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Tsikalov D. S.
Заглавие : High-Frequency Susceptibility of a Superlattice with 2D Inhomogeneities
Коллективы :
Разночтения заглавия :авие SCOPUS: High-frequency susceptibility of a superlattice with 2D inhomogeneities
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 107, Is. 4. - P603-611. - ISSN 1063-7761, DOI 10.1134/S1063776108100075
Примечания : Cited References: 26. - This work was supported in part by grant no. 3818.2008.3 from the President of Russia in accordance with the program supporting leading scientific schools.
Предметные рубрики: SPIN-WAVE SUSCEPTIBILITY
PERIODIC MULTILAYERS
LOCALIZATION
SYSTEMS
SPECTRUM
DISORDER
MEDIA
Ключевые слова (''Своб.индексиров.''): energy conservation--energy gap--energy management--frequency bands--gallium alloys--green's function--probability density function--three dimensional--band gaps--energy conservation laws--green functions--high frequencies--imaginary parts--magnon crystals--scattered waves--superlattice layers--wave spectrums--phase interfaces
Аннотация: We investigate the high-frequency susceptibility (Green function) of an initially sinusoidal 1D superlattice with 2D phase inhomogeneities that model the deformations of the interfaces between the superlattice layers. For waves propagating along the superlattice axis ( the geometry of a photon or magnon crystal), we have found a peculiar behavior of the imaginary part of the Green function that consists in a significant difference between the peaks corresponding to the edges of the band gap in the wave spectrum. The peak corresponding to the lower-frequency band edge remains essentially unchanged as the root-mean-square fluctuation of the 2D inhomogeneities. 2 increases, while the peak corresponding to the higher-frequency band edge broaden and decreases sharply in height until its complete disappearance with increasing gamma(2). This behavior of the peaks corresponds to a band gap closure mechanism that differs from the traditional one characteristic of 1D and 3D inhomogeneities. These effects can be explained by a peculiarity of the energy conservation laws for the incident and scattered waves for 2D inhomogeneities in a 1D superlattice.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Misyul S. V., Mel'nikova S. V., Bovina A. F., Laptash N. M.
Заглавие : Optical and X-ray Diffraction Studies of the Symmetry of Distorted Phases of the (NH4)(3)ZrF7 Crystal
Коллективы :
Разночтения заглавия :авие SCOPUS: Optical and x-ray diffraction studies of the symmetry of distorted phases of the (NH4)3ZrF7crystal
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 10. - P1951-1956. - ISSN 1063-7834, DOI 10.1134/S1063783408100272
Примечания : Cited References: 12. - This work was supported by the Council on Grants from the President of the Russian Federation (project NSh-4137.2006.2).
Предметные рубрики: AMMONIUM HEPTAFLUOROZIRCONATE
DISORDER
TRANSITION
K3ZRF7
Аннотация: (NH4)(3)ZrF7 single crystals were grown, and polarization-optical and x-ray diffraction studies were performed on powders and crystalline plates of various cuts over a wide temperature range. Phase transitions are revealed at temperatures T-1 up arrow = 280 K, T-2 up arrow = 279.6 K, T-3 up arrow = 260-265 K, and T-4 up arrow = 238 K on heating and at T-1 down arrow = 280 K, T-2 down arrow = 269-270 K, T-3 down arrow = 246 K, and T-4 down arrow = 235 K on cooling. The sequence of changes in symmetry is established to be as follows: O-h(5) (Z = 4)↔ D-2h(25) (Z = 2) ↔ C-2h(3) (Z = 2)↔ C-i(1) (Z = 108)↔ monoclinic(2) (Z = 216).
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Flerov I. N., Gorev M. V., Bogdanov E. V., Bovina A. F., Laptash N. M.
Заглавие : Thermophysical studies of the phase transitions in (NH4)(3)NbOF6 crystals
Разночтения заглавия :авие SCOPUS: Thermophysical studies of the phase transitions in (NH4) 3NbOF6 crystals
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 8. - P1548-1553. - ISSN 1063-7834, DOI 10.1134/S1063783407080240
Примечания : This work was supported by the Russian Foundation for Basic Research (project no. 06-02-16102), Krasnoyarsk Regional Science Foundation (project no.16G098), and the Council on Grants from President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (project NSh-4137.2006.2). - Cited References: 17
Предметные рубрики: OXYFLUORIDES
DISORDER
RB
CS
Аннотация: The thermophysical properties of oxyfluoride (NH4)(3)NbOF6 were studied in detail over wide ranges of temperatures and pressures. At atmospheric pressure, a sequence of four structural phase transitions was established with the following changes in entropy: Delta S (1) = Rln 2.7, delta S (2) = Rln38.3, Delta S (3) = 0.08R, and Delta S (4) = 0.17R. An external hydrostatic pressure was found to narrow the region of existence of the initial cubic phase. A triple point was detected in the p-T diagram; at a pressure above 0.07 GPa, the transition between the tetragonal and monoclinic phases occurs through a distorted high-pressure phase.
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