A universal order-disorder mechanism of structural phase transitions in A‘A”BX4 compounds

Authors:

• Michał Kurzyński

Abstract

A simple lattice model with two Ising spins is proved to explain almost all structural phase transitions observed in A‘A”BX4 compounds. Ising variables describe four discrete orientational states of BX4 tetrahedra. Symmetrical nearest neigh bour interactions between spins stabilize crystallographic structures with up to four formula units per elementary cell. Longer-period as well as incommensurate modulations of the order parameter, both along the hexagonal axis and in the perpendicular plane, originate either from next nearest neigh bour or, competitively, antisymmetrical nearest neigh bour interactions. © 1992, Taylor & Francis Group, LLC. All rights reserved.