High-pressure Phase Transition in CdTe by a Density Functional Lattice Dynamics Approach

An investigation of the stability of the metallic rocksalt structure with respect to the high pressure Cmcm structure for II-VI semiconductor CdTe was performed. The lattice dynamics calculations, based on density functional perturbation theory (DFPT), reveal that the rocksalt structure is unstable with respect to transversal acoustic mode at the Brillouin zone boundary. The phase transition is of the second order (zero volume change), associated with cell doubling in the high pressure Cmcm phase with frozen in deformation. The present calculations give the transition pressure more accurately than classical common tangent method. Since the volume change at the transition is very small or zero, the transition was estimated from the pressure at which the frequency of zone boundary transversal acoustic mode goes to zero. The observed pressure of the phase transition in structural measurements, reproduced more accurately than in previous experiments, differs from calculated transition pressure by about 15 %.