Constant pressure and temperature discrete-time Langevin molecular dynamics

TL;DR

This paper introduces a new discrete-time Langevin molecular dynamics method that accurately controls temperature and pressure, ensuring stable and statistically correct simulations across different time steps.

Contribution

The authors develop a novel set of discrete-time equations for particle and volume dynamics that improve pressure control robustness against time step variations.

Findings

Accurate statistical sampling demonstrated in benchmark systems.

Robust pressure control insensitive to time step size.

Outperforms previous methods like Kolb & Dunweg.

Abstract

We present a new and improved method for simultaneous control of temperature and pressure in molecular dynamics simulations with periodic boundary conditions. The thermostat-barostat equations are build on our previously developed stochastic thermostat, which has been shown to provide correct statistical configurational sampling for any time step that yields stable trajectories. Here, we extend the method and develop a set of discrete-time equations of motion for both particle dynamics and system volume in order to seek pressure control that is insensitive to the choice of the numerical time step. The resulting method is simple, practical, and efficient. The method is demonstrated through direct numerical simulations of two characteristic model systems - a one dimensional particle chain for which exact statistical results can be obtained and used as benchmarks, and a three dimensional system of Lennard-Jones interacting particles simulated in both solid and liquid phases. The results, which are compared against the method of Kolb & Dunweg, show that the new method behaves according to the objective, namely that acquired statistical averages and fluctuations of configurational measures are accurate and robust against the chosen time step applied to the simulation.