Study of the High-Pressure HCP Phase of Al: A Computer Aided Design and Simulation

Abstract

Based on the first-principles scheme, we have built several hcp-Al crystals and have calculated the lattice constants, cell volumes and elastic constants at high pressures using the plane-wave pseudo-potential method within ultrasoft pseudo-potentials. The basic thermal properties of Al are investigated by using the quasi-harmonic Debye model. The results show that the bulk moduli are still very large at high temperatures; hence hcp-Al can retain its stability at high pressure and high temperature. On the other hand, the temperature effects on the heat capacity and thermal expansion are significant. Several interesting phenomena have been observed in these quantities atT> 300K. More importantly, the negative shear moduli of hcp-Al indicate that our calculation results need to be verified by experiments in the near future.