Melting of pseudopotential sodium from molecular dynamics

For a pseudopotential model of metallic sodium, the Gibbs free energy of the fluid phase was calculated by a combination of molecular dynamics and the high-temperature free-energy expansion. From these calculations, together with previous molecular-dynamics results for crystalline sodium, the melting transition was determined as a function of pressure, up to 16 kbar. The pressure-temperature phase line is in good agreement with experiment, and so are the changes associated with melting at zero pressure, namely the heat of fusion, the entropy of fusion, and the relative volume change. The dynamic melting process, previously observed in molecular-dynamics simulations of sodium, is also in good agreement with the present equilibrium calculations.