An Isotropic Empirical Intermolecular Potential for Solid H_2 and D_2: A Classical Molecular Calculation

We develop an isotropic empirical potential for molecular hydrogen (H_2) and deuterium (D_2) by fitting to solid-state data, which is appropriate for classical molecular dynamics (CMD) approach. Based on the prior isotropic intermolecular potential used in self-consistent phonon approximation, a zero-point energy term and an embedded energy term are introduced to describe the H_2–H_2 and D_2–D_2 interactions in CMD simulations. The structure, cohesive energy and elastic properties of solid H_2 (D_2) are used as the fitting database. The present method is tested by calculating the melting point of solid H_2, and the pressure and bulk elastic modulus as a function of volume. The developed potentials well reproduce many properties of solid H_2 and D_2.