Equation of state of atomic solid hydrogen by stochastic many-body wave function methods

TL;DR

This study uses multiple advanced many-body wave function methods to accurately determine the equation of state of crystalline BCC hydrogen, providing reliable results through cross-method validation and extrapolation techniques.

Contribution

It applies and compares several stochastic and coupled-cluster methods to compute the equation of state of solid hydrogen, enhancing the reliability of theoretical predictions.

Findings

Agreement among methods for equilibrium lattice parameter

Lattice parameter determined as 3.307 Bohr

Demonstrates the effectiveness of combined stochastic and coupled-cluster approaches

Abstract

We report a numerical study of the equation of state of crystalline body-centered-cubic (BCC) hydrogen, tackled with a variety of complementary many-body wave function methods. These include continuum stochastic techniques of fixed-node diffusion and variational quantum Monte Carlo, and the Hilbert space stochastic method of full configuration-interaction quantum Monte Carlo. In addition, periodic coupled-cluster methods were also employed. Each of these methods is underpinned with different strengths and approximations, but their combination in order to perform reliable extrapolation to complete basis set and supercell size limits gives confidence in the final results. The methods were found to be in good agreement for equilibrium cell volumes for the system in the BCC phase, with a lattice parameter of 3.307 Bohr.