Thermodynamic properties of fluid sodium from molecular dynamics

The high-temperature thermodynamic properties of metallic fluid sodium were calculated from melting to a temperature $T=2200$ K. A pseudopotential model was used that consisted of a large volume-dependent potential plus a small effective two-body potential. Using molecular-dynamics calculations for the ionic motions and including electronic excitation contributions, we have determined the zero-pressure volume versus temperature curve, the adiabatic bulk modulus, the heat capacities at constant pressure and volume, and the thermodynamic Gr\"uneisen parameter. We find our theory to be in excellent agreement with experiment up to $T=1200$ K, but note a significant deviation at higher temperatures.