High pressure phase transition and elastic behavior of TlX (X=N, P, As) semiconductors

We have investigated the pressure induced phase transition from zinc-blend (B3) to rock-salt (B1) structure, associated volume collapses and elastic properties of TlX (X=N, P, As) semiconductors by using an interaction potential model (IPM) based on the charge transfer effect. The IPM consists of Coulomb interaction, three-body interaction, short-range overlap repulsive interaction up to second neighbor ions, van der Waal's interactions and zero point energy effect The present theoretical approach has predicted pressure-volume relationship curves which show that TlN, TlP and TlAs exhibit a zinc-blend (ZB) type structure at an ambient pressure and undergo a structural phase transition from B3 to B1 phase at 20, 7.2 and 5 GPa. The phase transition pressure and associated volume collapses obtained from this model show a reasonable agreement with other theoretical results. The second order elastic constants and variation of second order elastic constants with pressure for ZB phase are presented. We have also calculated some elastic properties such as anisotropy factor, Young modulus, Poisson ratio and sound velocities. Many thermodynamic properties are also presented. (C) 2012 Elsevier Ltd. All rights reserved.