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Structural Phase Transitions in Langbeinites
Author(s) -
Dvořák V.
Publication year - 1972
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.2220520110
Subject(s) - brillouin zone , condensed matter physics , phase transition , ferroelectricity , landau theory , superconductivity , phonon , phase (matter) , homogeneous , instability , physics , materials science , quantum mechanics , statistical physics , dielectric
Using Landau theory of phase transitions it is shown that in the langbeinite structure (space group T 4 ) four spatially homogeneous structural phase transitions are possible. Theree of them are improper ferroelectric and result from a phonon instability at the M point of the Brillouin zone. The fourth one is very similar to structural phase transitions in hig temperature superconductors of the β‐tungsten structure. The free energies providing a basis for macroscopic description of these phase transitions are presented.