Equation of state and sound velocity of a helium plasma by Thomas-Fermi-Dirac molecular dynamics

A method combining classical molecular dynamics applied to nuclei and Thomas-Fermi-Dirac theory applied to electrons is used to calculate the thermodynamic properties of an helium plasma. Two densities, corresponding to average electronic radii of 1 and 2 Bohr radii, and several temperatures, corresponding to coupling parameters between 0.1 and 100, are considered. Both pressure and internal energy (with a correction for the regularization of the potential) are obtained. Some derivative quantities and sound velocity are computed by numerical differentiation with a careful evaluation of the truncation error and of the statistical error. Pressure and sound velocity are obtained with relative standard deviations, respectively, of less than 0.3% and 2.5%.