Interaction Potentials and Equation of State of Solid Deuterium: a Path Integral Monte Carlo Study

Within a movable and orientable rigid rotor model, four interaction potentials of solid deuterium (hydrogen) system from combinations of two isotropic and two anistropic parts are tested by the path integral Monte Carlo method in a constant-pressure ensemble. With the best one of the potentials, the equation of state of deuterium is quantitatively in agreement with the experimental data. For understanding the quantum nature of the solid, the energies of the system at different temperatures are also calculated, the results show strong zero-point motions exist in the solid. As would be expected, the quantum corrections to both the rotational and the translational kinetic energies decrease with increasing temperature, and increase with pressure.