Quantum Monte Carlo, Density Functional Theory, and Pair Potential Studies of Solid Neon

TL;DR

This study compares quantum Monte Carlo, density functional theory, and pair potential methods to accurately model the zero-temperature equation of state of solid neon, highlighting QMC's superior treatment of van der Waals forces.

Contribution

The paper demonstrates that QMC provides a more accurate EOS for solid neon than DFT and pair potentials, especially at high densities, and introduces a new pair potential derived from QMC data.

Findings

QMC EOS closely matches experimental data and outperforms DFT and pair potentials.

QMC accurately models van der Waals interactions in solid neon.

New pair potential derived from QMC data improves EOS predictions.

Abstract

We report quantum Monte Carlo (QMC), plane-wave density-functional theory (DFT), and interatomic pair-potential calculations of the zero-temperature equation of state (EOS) of solid neon. We find that the DFT EOS depends strongly on the choice of exchange-correlation functional, whereas the QMC EOS is extremely close to both the experimental EOS and the EOS obtained using the best semiempirical pair potential in the literature. This suggests that QMC is able to give an accurate treatment of van der Waals forces in real materials, unlike DFT. We calculate the QMC EOS up to very high densities, beyond the range of values for which experimental data are currently available. At high densities the QMC EOS is more accurate than the pair-potential EOS. We generate a different pair potential for neon by a direct evaluation of the QMC energy as a function of the separation of an isolated pair of neon atoms. The resulting pair potential reproduces the EOS more accurately than the equivalent potential generated using the coupled-cluster CCSD(T) method.