Nuclear Quantum Effects and Nonlocal Exchange-Correlation Functionals Applied to Liquid Hydrogen at High Pressure

TL;DR

This study demonstrates that nuclear quantum effects and advanced nonlocal exchange-correlation functionals significantly improve the accuracy of simulations of liquid hydrogen under high pressure, especially in predicting dissociation and metallization.

Contribution

It introduces the combined use of nuclear quantum effects and nonlocal density functionals in first-principles molecular dynamics to better model liquid hydrogen at high pressures.

Findings

NQEs strongly affect bond stability and dissociation.

Advanced DFs improve agreement with experimental optical data.

Transition pressures for liquid-liquid transition increase by over 100 GPa.

Abstract

Using first-principles molecular dynamics, we study the influence of nuclear quantum effects (NQEs) and nonlocal exchange--correlation density functionals (DFs) near molecular dissociation in liquid hydrogen. NQEs strongly influence intramolecular properties, such as bond stability, and are thus an essential part of the dissociation process. Moreover, by including DFs that account for either the self-interaction error or dispersion interactions, we find a much better description of molecular dissociation and metallization than previous studies based on classical protons and/or local or semi-local DFs. We obtain excellent agreement with experimentally measured optical properties along pre-compressed Hugoniots, and while we still find a first-order liquid--liquid transition at low temperatures, transition pressures are increased by more than 100 GPa.