Molecular-dynamics study of melting on the shock Hugoniot of Al

We investigate the Hugoniot melting point of Al using a molecular-dynamics approach based on an embedded-atom method. We calculate the Gibbs free ener gies of the crystalline and liquid phases as a function of pressure and tem perature using the coupling-constant integration method and obtain the melt ing curve up to 1.6 Mbar, in good agreement with experiments. We also exami ne the melting properties near zero pressure. The Hugoniot equation of stat es (EOS) up to 1.8 Mbar is obtained from the Rankine-Hugoniot relation and the isotherms determined for different temperatures. Comparing the melting curve with the Hugoniot EOS's for the solid and liquid phases, the Hugoniot melting is found to begin at 1.2 Mbar and to end at 1.4 Mbar, consistent w ith shock-wave data. [S0163-1829(99)02301-2].