Перевод заглавия: Последовательность фазовых переходов в (NH4)3SiF7
Кл.слова (ненормированные):
Group theory -- Single crystals -- X ray diffraction -- Atomic displacement -- Double salts -- Driving forces -- Group-theoretical analysis -- Order parameter -- Polarization optics -- Temperature changes -- Hydrogen bonds
Аннотация: Single crystals of silicon double salt (NH4)3SiF7 = (NH4)2SiF6·NH4F = (NH4)3[SiF6]F were grown and studied by the methods of polarization optics, X-ray diffraction and calorimetry. A sequence of symmetry transformations with the temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ P1 (Z = 4) (G4) ↔ P21/c (Z = 8) (G5). Crystal structures of different phases were determined. The experimental data were also interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account critical and noncritical atomic displacements. Strengthening of the N–H⋯F hydrogen bonds can be a driving force of the observed phase transitions.
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Держатели документа:
Laboratory of Crystal Physics, Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Department of Physics, Far Eastern State Transport University, Khabarovsk, Russian Federation
Institute of Chemistry, Far Eastern Branch of RAS, Vladivostok, Russian Federation
Siberian Federal University, Krasnoyarsk, Russian Federation
Доп.точки доступа:
Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Molokeev, M. S.; Молокеев, Максим Сергеевич; Laptash, N. M.; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Misyul, S. V.; Flerov, I. N.; Флёров, Игорь Николаевич