Solidification of small para-H2 clusters at zero temperature

TL;DR

This study uses diffusion Monte Carlo simulations to analyze the phase behavior of small para-H2 clusters at zero temperature, revealing inhomogeneous crystallization and phase transitions.

Contribution

It provides the first detailed ground-state energy calculations for para-H2 clusters up to N=75, identifying their stable phases and phase transition behavior.

Findings

Clusters exhibit inhomogeneous crystallization with alternating phases up to N=55.

All clusters with N>55 are solid.

Density profiles differ significantly between liquid and solid phases, aiding phase identification.

Abstract

We have determined the ground-state energies of para-H$_2$ clusters at zero temperature using the diffusion Monte Carlo method. The liquid or solid character of each cluster is investigated by restricting the phase through the use of proper importance sampling. Our results show inhomogeneous crystallization of clusters, with alternating behavior between liquid and solid phases up to N=55. From there on, all clusters are solid. The ground-state energies in the range N=13--75 are established and the stable phase of each cluster is determined. In spite of the small differences observed between the energy of liquid and solid clusters, the corresponding density profiles are significantly different, feature that can help to solve ambiguities in the determination of the specific phase of H$_2$ clusters.