Z methodology for phase diagram studies: platinum and tantalum as examples

Abstract

The Z methodology is a novel technique for phase diagram studies. It combines the direct Z method for the computation of melting curves and the inverse Z method for the calculation of solid-solid phase boundaries. In the direct Z method, the solid phases along the melting curve are determined by comparing the solid-liquid equilibrium boundaries of candidate crystal structures. The inverse Z method involves quenching the liquid into the most stable solid phase at various temperatures and pressures to locate a solid-solid boundary. The direct and inverse Z methods in conjunction with the VASP ab initio molecular dynamics package are used to investigate the phase diagrams of tantalum and platinum. We compare our results to the most recent experimental data.