Theoretical compressibilities of high-pressure ZnTe polymorphs

R. Franco, P. Mori-Sa´nchez, and J. M. Recio*

Departamento de Quı´mica Fı´sica y Analı´tica, Universidad de Oviedo, E-33006 Oviedo, Spain

R. Pandey

Physics Department, Michigan Technological University, Houghton, Michigan 49931, USA

~Received 12 June 2003; published 20 November 2003!

Abstract

 We report the results of a theoretical study of structural, electronic, and pressure-induced phase transition properties in ZnTe. Total energies of several high-pressure polymorphs are calculated using the density functional theory ~DFT! formalism under the nonlocal approximation. Thermal effects are included by means of a nonempirical Debye-like model. In agreement with optical absorption data, the lowest direct gap of the zinc blende polymorph is found to follow a nonlinear pressure dependence that turns into linear behavior when expressed in terms of the decrease in the lattice parameter. The pressure stability ranges of cubic ~zinc blende and rocksalt!, trigonal ~cinnabar!, and orthorhombic ~Cmcm! polymorphs are computed at static and room temperature conditions. Our calculations agree with the experimental and theoretical reported zinc blende →cinnabar→Cmcm pressure-induced phase sequence. Linear and bulk compressibilities are evaluated for the four polymorphs and reveal an anisotropic behavior of the cinnabar structure, which contrasts with the cubiclike compression of its shortest Zn-Te bonds. The qualitative trend shows a crystal that becomes relatively less compressible in the high-pressure phases.

http://www.phy.mtu.edu/pandey/publications/FMRP2003.pdf