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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Voronov V. N.
Заглавие : Entropy of Rb2KB3+F6 (B3+: Se, In, Lu, Er, Ho) ferroelastics and the triple point on T(R(B)(3+)) diagram
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1996. - Vol. 38, Is. 3. - P717-727. - ISSN 0367-3294
Примечания : Cited References: 26
Предметные рубрики: STRUCTURAL PHASE-TRANSITIONS
RB2KMIIIF6 ELPASOLITES
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V.
Заглавие : Entropy and the mechanism of phase transitions in elpasolites
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2001. - Vol. 43, Is. 1. - P127-136. - ISSN 1063-7834, DOI 10.1134/1.1340198
Примечания : Cited References: 33
Предметные рубрики: ORDERED PEROVSKITE PB2MGTEO6
ELASTIC NEUTRON-DIFFRACTION
THERMODYNAMIC PROPERTIES
CUBIC PEROVSKITES
CRYSTAL-STRUCTURE
HIGH-RESOLUTION
PB2MGWO6
CSPBCL3
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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Tressaud A., Durand E.
Заглавие : The p-T phase diagram of ammonium hexafluoroaluminate
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2002. - Vol. 14, Is. 25. - P6447-6453. - ISSN 0953-8984, DOI 10.1088/0953-8984/14/25/312
Примечания : Cited References: 17
Предметные рубрики: NUCLEAR MAGNETIC-RESONANCE
TRANSITIONS
MOTIONS
F-19
H-1
Ключевые слова (''Своб.индексиров.''): entropy--hydrostatic pressing--mathematical models--order disorder transitions--phase diagrams--specific heat of solids--ammonium hexafluoroaluminate--crolite--elpasolite--ammonium compounds
Аннотация: The heat capacity and the effect of hydrostatic pressure on structural phase transitions in ammonium hexafluoroaluminate, (NH4)(3)AlF6, have been studied. Two heat capacity anomalies have been found with maxima at T-1 = 218.5 +/- 0.5 K and T-2 = 179 +/- 2 K. Respective entropy changes of phase transitions are DeltaS(1) = 15.3 +/- 0.5 J mol(-1) K-1 and DeltaS(2) = 2.5 +/- 0.5 J mol(-1) K-1. It is shown that the p-T phase diagram of this compound is rather complex and contains a triple point (p(tp) = 0.12 GPa, T-tp = 221 K) and high-pressure phase. The mechanism of transformations and generalized p-T phase diagram for compounds of the (NH4)(3)(MF6)-F-III family are discussed within the framework of the rotational order-disorder model.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorban A., Popova T., Zinovyev A.
Заглавие : Codon usage trajectories and 7-cluster structure of 143 complete bacterial genornic sequences
Разночтения заглавия :авие SCOPUS: Codon usage trajectories and 7-cluster structure of 143 complete bacterial genomic sequences
Место публикации : Physica A: ELSEVIER SCIENCE BV, 2005. - Vol. 353. - P365-387. - ISSN 0378-4371, DOI 10.1016/j.physa.2005.01.043
Примечания : Cited References: 46
Предметные рубрики: DNA-BASE COMPOSITION
ASYMMETRIC SUBSTITUTION PATTERNS
PROTEIN-CODING REGIONS
MICROBIAL GENOMES
GENE IDENTIFICATION
MARKOV-MODELS
G+C CONTENT
BIAS
PREDICTION
SELECTION
Ключевые слова (''Своб.индексиров.''): genome--cluster--codon usage--correlations--entropy--mean field--cluster--codon usage--correlations--entropy--genome--mean field--approximation theory--correlation methods--database systems--entropy--functions--genes--mathematical models--clusters--codon usage--genomes--mean field--bacteria
Аннотация: Three results are presented. First, we prove the existence of a universal 7-cluster structure in all 143 completely sequenced bacterial genomes available in Genbank in August 2004, and explained its properties. The 7-cluster structure is responsible for the main part of sequence heterogeneity in bacterial genomes. In this sense, our 7 clusters is the basic model of bacterial genome sequence. We demonstrated that there are four basic "pure" types of this model, observed in nature: "parallel triangles", "perpendicular triangles", degenerated case and the flower-like type. Second, we answered the question: how big are the position-specific information and the contribution connected with correlations between nucleotide. The accuracy of the mean-field (context-free) approximation is estimated for bacterial genomes. We show that codon us-age of bacterial genomes is a multi-linear function of their genomic G+C-content with high accuracy (more precisely, by two similar functions, one for eubacterial genomes and the other one for archaea). Description of these two codon-usage trajectories is the third result. All 143 cluster animated 3D-scatters are collected in a database and is made available on our web-site: http://www.ihes.fr/similar to zinovyev/7clusters. (c) 2005 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. N., Popova E. A., Bezmaternykh L. N., Temerov V. L., Hiroi Z.
Заглавие : Specific heat of YFe3(BO3)(4), Y0.5Gd0.5Fe3(BO3)(4), and GdFe3(BO3)(4)
Разночтения заглавия :авие SCOPUS: Specific heat of YFe3(BO3)4, Y 0.5Gd0.5Fe3(BO3)4, and GdFe3(BO3)4
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 2. - P262-265. - ISSN 1063-7761, DOI 10.1134/S1063776106020075
Примечания : Cited References: 10
Предметные рубрики: TRIGONAL GDFE3(BO3)(4)
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--gadolinium compounds--heat transfer--ions--magnetic fields--single crystals--temperature measurement--yttrium compounds--magnetic entropy--magnetic system--reorientational transitions--scaling procedure--specific heat of solids
Аннотация: The specific heat was measured in the range 0.4-300 K in YFe3(BO3)(4), Y0.5Gd0.5Fe3(BO3)(4), and GdFe3(BO3)(4) single crystals. Sharp anomalies were found at temperatures of first-order structural, second-order antiferromagnetic, and first-order spin-reorientational transitions. A Neel temperature of about 37 K was found to be virtually independent of presence of rare-earth ions, indicating rather weak coupling of Gd and Fe subsystems. The contribution of the magnetic system to specific heat was separated through the scaling procedure allowing determination of the magnetic entropy of Fe and Gd subsystems. At the lowest temperatures, the specific heat in GdFe3(BO3)(4) exhibits a Schottky-type anomaly, which is due to Gd3+ eightfold degenerate ground-level splitting by the internal magnetic field of the Fe subsystem of about 7 T.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Sablina K. A., Eremin E. V., Boni P., Shah V. R., Flerov I. N., Kartashev A., Rasch JCE, Boehm M., Schefer J.
Заглавие : Heat capacity of a mixed-valence manganese oxide Pb(3)Mn(7)O(15)
Коллективы :
Разночтения заглавия :авие SCOPUS: Heat capacity of a mixed-valence manganese oxide Pb3Mn 7O15
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2008. - Vol. 20, Is. 44. - Ст.445214. - ISSN 0953-8984, DOI 10.1088/0953-8984/20/44/445214
Примечания : Cited References: 11. - This study was supported by the INTAS (project No 061000013-9002), the Division of Physical Sciences of RAS, program `Spin-dependent Effects in Solids and Spintronics' (project No. 2.4.2 of SB RAS), the President of the Russian Federation, grant for Support of Leading Scientific Schools (project No. NSh-1011.2008.2), KRSF-RFBR `Enisey2007', project No. 07-02-96801-a, and the Siberian Branch of RAS, Integration project No. 3.7.
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--crystallography--entropy--lead alloys--magnetic materials--magnetism--manganese--manganese compounds--powders--single crystals--specific heat--spin dynamics--antiferromagnetic orders--charge localizations--entropy losses--excess heat capacities--experimental datums--heat capacities--magnetic contributions--magnetic orders--magnetic states--magnetic subsystems--magnetic transitions--manganese oxides--nonmagnetic--spin systems--temperature curves--temperature dependences--temperature intervals--temperature ranges--manganese alloys
Аннотация: We present the results of a heat capacity study of Pb(3)Mn(7)O(15) single crystals with approximately equal concentrations of Mn(3+) and Mn(4+) ions. In the temperature interval between 210 and 260 K, an excess heat capacity of nonmagnetic origin, most likely associated with the process of charge localization, has been observed. Also, three pronounced anomalies corresponding to the changes in a magnetic subsystem of the crystal have been observed in the temperature dependence of the heat capacity. A broad hump near 150 K is related to the formation of a short-range magnetic order. This process of short-range ordering is rather prominent, considering the appreciable value of the entropy loss accompanying the change in the magnetic state. A clear lambda-shaped peak at 70 K marks the onset of a long-range antiferromagnetic order. Another anomalous contribution to the heat capacity of magnetic origin has been revealed at temperatures below 20 K. This contribution is associated with a magnetic transition of an unknown nature, which is also clearly evident in magnetization versus temperature curves. The total magnetic contribution to the entropy deduced from the actual experimental data over the entire temperature range is much smaller than is expected for a completely ordered Mn spin system in the crystal. We suggest several possible reasons that may account for this `missing' entropy.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Fokina V. D., Bovina A. F., Bogdanov E. V., Pogoreltsev E. I., Laptash N. M.
Заглавие : Disorder and phase transitions in oxyfluoride (NH4)(3)Ta(O-2)(2)F-4
Место публикации : J. Fluor. Chem. - 2011. - Vol. 132, Is. 10. - P.713-718. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2011.05.012
Примечания : Cited Reference Count: 19. - Гранты: This work was supported by 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).Финансирующая организация: 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]
Предметные рубрики: HEAT-CAPACITY
COMPLEXES
RB2KTIOF5
FLUORIDES
CRYOLITE
Ключевые слова (''Своб.индексиров.''): cubic oxyfluorides--structural disorder--phase transitions--entropy--permittivity--pressure effect--cubic oxyfluorides--entropy--permittivity--phase transitions--pressure effect--structural disorder
Аннотация: Calorimetric, X-ray, dielectric and DTA under pressure measurements have been performed on oxyfluoride (NH4)(3)Ta(O-2)(2)F-4. The succession of nonferroelectric phase transitions was found associated with the order-disorder processes. The comparative analysis tantalate with related niobate has revealed the important role of the central atom in the physical properties behavior, mechanism of structural distortions and barocaloric effect in oxyfluorides with the eight-coordinated anionic polyhedra. (C) 2011 Elsevier By. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Gorev M. V., Bogdanov E. V., Pogoreltsev E. I., Flerov I. N., Laptash N. M.
Заглавие : Thermal properties and phase transitions in (NH4) 3ZrF7
Место публикации : Journal of Fluorine Chemistry. - 2013. - Vol. 154. - P.1-6. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2013.07.001
Ключевые слова (''Своб.индексиров.''): cubic fluorides--entropy--permittivity--phase transitions--pressure effect--thermal dilatation
Аннотация: The heat capacity, thermal dilatation, permittivity, and T-p phase diagram of (NH4)3ZrF7 have been studied in wide temperature and pressure ranges. Two phase transitions were found in addition to previously known structural transformations. The stability of crystal phases to temperature and pressure has been examined and a possibility of transition between two cubic phases has been discussed. The total excess entropy change SDSi = Rln6 is characteristic for the order-disorder processes, but its stepwise increase is not consistent with the structural model associated with the strong disorder assumed in the initial cubic phase. В© 2013 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogoreltsev E. I., Flerov I. N., Kartashev A. V., Bogdanov E. V., Laptash N. M.
Заглавие : Heat capacity, entropy, dielectric properties and T–p phase diagram of (NH4)3TiF7
Коллективы : Russian Foundation for Basic Research [15-02-02009]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]
Место публикации : J. Fluor. Chem.: Elsevier Science, 2014. - Vol. 168. - P.247-250. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.10.016. - ISSN 1873-3328
Примечания : Cited References: 16. - This work was supported by the Russian Foundation for Basic Research (Grant no. 15-02-02009), and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (Grant no. NSh-924.2014.2).
Предметные рубрики: CRYSTAL-STRUCTURE
TRANSITIONS
FLUORIDES
NH4F
Ключевые слова (''Своб.индексиров.''): cubic fluorides--phase transitions--dielectric--phase diagram--calorimetry
Аннотация: Successive phase transitions G1 -- G2 -- G3 in the double salt (NH4)(3)TiF7 have been studied by detailed calorimetric, DTA under hydrostatic pressure and dielectric measurements. Rather large entropy jumps at phase transition points were found to be followed by large additional contributions associated with the temperature dependence of the excess heat capacity. The permittivity behaviour and the tangent of the dielectric losses proved the nonferroelectric nature of both transformations. Two triple-points were found on the temperature-pressure phase diagram, suggesting the existence of a hypothetical parent G0 = Pm-3m cubic phase. A direct transformation between high (G0) and low (G3) temperature cubic phases takes place at p 0.41 GPa with a baric coefficient dT(G0) -- (G3)/dp = -40 K/GPa. (C) 2014 Elsevier B.V. All rights reserved.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kartashev A. V., Gorev M. V., Bogdanov E. V., Flerov I. N., Laptash N. M.
Заглавие : Thermal properties and phase transition in the fluoride, (NH4)3SnF7
Место публикации : J. Solid State Chem. - 2016. - Vol. 237. - P.269-273. - ISSN 00224596 (ISSN), DOI 10.1016/j.jssc.2016.02.027
Примечания : Cited References: 18. - This study was partially supported by the Russian Foundation for Basic Research (RFBR), research Project no. 15-02-02009a.
Предметные рубрики: Heat-capacity
Chemistry
Ключевые слова (''Своб.индексиров.''): phase transition--fluorides--heat capacity--entropy--thermal expansion--high pressure
Аннотация: Calorimetric, dilatometric and differential thermal analysis studies were performed on (NH4)3SnF7 for a wide range of temperatures and pressures. Large entropy (δS0=22 J/mol K) and elastic deformation (δ(ΔV/V)0=0.89%) jumps have proven that the Pa-3虠Pm-3m phase transition is a strong first order structural transformation. A total entropy change of ΔS0=32.5 J/mol K is characteristic for the order-disorder phase transition, and is equal to the sum of entropy changes in the related material, (NH4)3TiF7, undergoing transformation between the two cubic phases through the intermediate phases. Hydrostatic pressure decreases the stability of the high temperature Pm-3m phase in (NH4)3SnF7, contrary to (NH4)3TiF7, characterised by a negative baric coefficient. The effect of experimental conditions on the chemical stability of (NH4)3SnF7 was observed. © 2016 Elsevier Inc.
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