Accelerated ab-initio Molecular Dynamics: probing the weak dispersive forces in dense liquid hydrogen

TL;DR

This paper introduces a novel accelerated ab-initio molecular dynamics method that significantly reduces simulation autocorrelation times, enabling detailed study of dense liquid hydrogen and its phase transitions.

Contribution

The authors develop a new Langevin dynamics-based approach with a position-dependent acceleration matrix, improving simulation efficiency for quantum and classical particles.

Findings

The method allows equilibration in a few hundred steps near phase transitions.

Results suggest long-range dispersive forces influence the liquid-liquid transition pressure.

Simulations extend beyond previous autocorrelation time limitations.

Abstract

We propose an ab-initio molecular dynamics method, capable to reduce dramatically the autocorrelation time required for the simulation of classical and quantum particles at finite temperature. The method is based on an efficient implementation of a first order Langevin dynamics modified by means of a suitable, position dependent acceleration matrix $S$. Here we apply this technique, within a Quantum Monte Carlo (QMC) based wavefuntion approach and within the Born-Oppheneimer approximation, for determining the phase diagram of high-pressure Hydrogen with simulations much longer than the autocorrelation time. With the proposed method, we are able to equilibrate in few hundreds steps even close to the liquid-liquid phase transition (LLT). Within our approach we find that the LLT transition is consistent with recent density functionals predicting a much larger transition pressures when the long range dispersive forces are taken into account.