LDA simulations of pressure-induced anomalies in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi><mml:mo>/</mml:mo><mml:mi>a</mml:mi></mml:math>and electric-field gradients for Zn and Cd

Abstract

We present results of ab initio simulations of the effect of hydrostatic pressure on the electronic structure, lattice parameters, and electric-field gradients (EFG) for hcp Zn and Cd using the full-potential linear muffin-tin orbital method in conjunction with the new Perdew-Burke-Ernzerhof generalized gradient approximation (GGA) to the density functional for exchange correlation. Theoretical equilibrium volumes for Zn and Cd are found to be in excellent agreement with experiment (whereas non-GGA corrected local density approximation underestimates them by as much as 10%). We find an anomaly in the pressure dependence of $c/a$ at reduced unit cell volumes (at ${V/V}_{0}\ensuremath{\simeq}0.89$ for Zn and in a broad region from ${V/V}_{0}=0.92$ to 0.85 for Cd) and a similar anomaly in the EFG tensor. At the same time we do not find the electronic topological transition due to the destruction of a giant Kohn anomaly which was previously thought to be responsible for the lattice anomalies in Zn.