Structural phase transition in CH3 NH3 Cd Br3 crystal. Pseudospin description using group theory
Written by sctunisie no commentsThe crystal of CH3NH3CdBr3 exhibits an order disorder phase transition at 170 K from an hexagonal (Z = 2) to a complex orthorhombic (Z = 96) structure . A six dimensional pseudo spin model is tentatively used to describe the mechanism of this phase transition. Pseudo-spin coordinates, associated to the orientational disorder of the methylammonium groups in the hexagonal phase, are determined at different points of the Brillouin's zone. Coupling processes between these coordinates are able to provide possible solutions for the structure of the "projection" unit cell with Z = 12 , that could be taken as starting hypotheses for the structure determination of the complex unit cell of the low temperature phase.
A. Kallel, Y. Mlik
Pages 907-921
