On the hierarchical parallelization of ab initio simulations

TL;DR

This paper introduces a hierarchical parallelization approach in the PIMD-SMASH code, enabling efficient ab initio molecular dynamics simulations of small water systems and studying solvent effects on a Diels-Alder reaction.

Contribution

It presents a new hierarchical parallelization method in a unified code for ab initio simulations, improving efficiency for small systems and applying it to reaction studies.

Findings

Efficient ab initio path integral simulations for systems up to tens of water molecules.

Hydrogen-bonded water reduces the reaction energy barrier in the studied Diels-Alder reaction.

The results align with experimental observations.

Abstract

A hierarchical parallelization has been implemented in a new unified code PIMD-SMASH for ab initio simulation where the replicas and the Born-Oppenheimer forces are parallelized. It is demonstrated that ab initio path integral molecular dynamics simulations can be carried out very efficiently for systems up to a few tens of water molecules. The code was then used to study a Diels-Alder reaction of cyclopentadiene and butenone by ab initio string method. A reduction in the reaction energy barrier is found in the presence of hydrogen-bonded water, in accordance with experiment.