Pair potentials and equation of state of solid parahydrogen to megabar pressure

TL;DR

This study uses Quantum Monte Carlo simulations to compute the equation of state of solid parahydrogen up to 2 MBar, comparing three pair potentials, with the Moraldi potential showing excellent agreement with experimental data.

Contribution

It introduces a modified Moraldi pair potential with a repulsive core that accurately predicts the equation of state at megabar pressures.

Findings

Moraldi potential agrees well with experimental data at high pressures

The Moraldi potential is as accurate as traditional potentials at vapor pressure

Kinetic energy estimates are provided for all potentials

Abstract

We compute by means of Quantum Monte Carlo simulations the equation of state of bulk solid {para}hydrogen extrapolated to zero temperature, up to a pressure of ~ 2 MBar. We compare the equation of state yielded by three different pair potentials, namely the Silvera-Goldman, Buck and one recently proposed by Moraldi, modified at short distances to include a repulsive core, missing in the originally proposed potential. The Moraldi pair potential yields an equation of state in very good agreement with experiment at megabar pressures, owing to its softer core, and is at least as accurate as the SG or the Buck at saturated vapour pressure. Estimates for the experimentally measurable kinetic energy per molecule are provided for all pair potentials.