Canonical-ensemble extended Lagrangian Born-Oppenheimer molecular dynamics for the linear scaling density functional theory

TL;DR

This paper introduces a new canonical-ensemble extended Lagrangian Born-Oppenheimer molecular dynamics method that combines linear scaling DFT with thermostats, ensuring stable energy conservation in simulations of silicon systems.

Contribution

It develops and tests a novel integration scheme for canonical-ensemble extended Lagrangian BOMD using linear scaling DFT, maintaining stability and energy conservation.

Findings

Stable conserved quantity with no systematic drift

Effective simulation of bulk silicon and silicon carbide

Integration scheme compatible with thermostats

Abstract

We discuss the development and implementation of a constant temperature (NVT) molecular dynamics scheme that combines the Nos\'e-Hoover chain thermostat with the extended Lagrangian Born-Oppenheimer molecular dynamics (BOMD) scheme, using a linear scaling density functional theory (DFT) approach. An integration scheme for this canonical-ensemble extended Lagrangian BOMD is developed and discussed in the context of the Liouville operator formulation. Linear scaling DFT canonical-ensemble extended Lagrangian BOMD simulations are tested on bulk silicon and silicon carbide systems to evaluate our integration scheme. The results show that the conserved quantity remains stable with no systematic drift even in the presence of the thermostat.