Перевод заглавия: Необычная последовательность фазовых переходов в (NH4)3GeF7: Оптическое и структурное исследование
Аннотация: Single crystals of germanium double salt (NH4)3GeF7 = (NH4)2GeF6·NH4F = (NH4)3[GeF6]F were grown and studied by the methods of polarization optics and X-ray diffraction. The birefringence Δn = (no − ne), the rotation angle of the optical indicatrix ϕ(T) and unit cell parameters were measured in the temperature range 100–400 K. Three structural phase transitions were found at the temperatures: T1↓ = 279.2 K (T1↑ = 279.4 K), T2↑ = 270 K (T2↓ = 268.9 K), T3↓ = 218 K (T3↑ = 227 K). An unusual sequence of symmetry transformations with temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ Pa (Z = 8) (G4). The crystal structures of different phases were determined. The experimental data were additionally interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account the critical and noncritical atomic displacements. Strengthening of the N–H⋯F hydrogen bonds can be a driving force of the observed phase transitions.
Смотреть статью,
Scopus,
WOS,
Для получение полного текста обратитесь в библиотеку
Держатели документа:
SB RAS, Lab Crystal Phys, Kirensky Inst Phys, Krasnoyarsk 660036, Russia.
Far Eastern State Transport Univ, Dept Phys, Khabarovsk 680021, Russia.
RAS, Inst Chem, Far Eastern Branch, Vladivostok 690022, Russia.
Siberian Fed Univ, Krasnoyarsk 660074, Russia.
Доп.точки доступа:
Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Molokeev, M. S.; Молокеев, Максим Сергеевич; Laptash, N. M.; Misyul, S. V.; Мисюль, Сергей Валентинович; RFBR [15-02-02009 a]