Variational Path Integral Molecular Dynamics Study of Small Para-Hydrogen Clusters

Abstract

In the present study, energetics of small para-hydrogen clusters has been investigated by the variational path integral molecular dynamics method, which generates numerically the exact ground state of many-body systems. Cluster sizes used range from N = 4 to N = 20. While in a classical approximation the chemical potential of the hydrogen molecule has three minima in the size dependence, the quantum kinetic energy is found to wash out the minima except at N = 13. The chemical potential is decomposed into two contributions: one is from the quantum kinetic energy and the other from the potential energy. These two contributions tend to cancel out and generate a shallow minimum in the size dependence at N = 13. On the basis of the inherent structure analysis, the size dependence of the contribution from the potential energy is well described by the underlying potential energy landscape sampled by the quantum kinetic energy.