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On Phase Transitions in LiNH 4 SO 4
Author(s) -
Torgashev V. I.,
Dvořák V.,
Smutný F.
Publication year - 1984
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221260204
Subject(s) - phase diagram , monoclinic crystal system , phase transition , raman spectroscopy , phase (matter) , landau theory , diagram , spectral line , thermodynamics , physics , materials science , mathematics , statistics , optics , quantum mechanics , molecule
A Landau‐type thermodynamie theory describing the sequence of phase transitions in lithium ammonium sulphate at atmospheric pressure is developed. The form of the phase diagram is derived and compared with that constructed on the basis of published experimental data. The existence of a new monoclinic high pressure phase is proposed. Formulae for permittivity are presented and compared with available experimental data. Soft mode features of Raman and infra‐red spectra are briefly discussed.