Kinetic Energy-Based Temperature Computation in Non-Equilibrium Molecular Dynamics Simulation

TL;DR

This paper investigates different kinetic energy measures for temperature calculation in non-equilibrium molecular dynamics, finding that thermal disturbance kinetic energy provides more accurate and applicable results, especially with a calibration method for small samples.

Contribution

The study introduces a calibration approach for thermal disturbance kinetic energy to accurately compute local temperature in non-equilibrium MD simulations.

Findings

Thermal disturbance kinetic energy yields realistic temperature estimates.

Rigid motion-based kinetic energies can produce unrealistic results.

Calibration reduces sample-size dependence in local temperature measurements.

Abstract

The average kinetic energy is widely used to characterize temperature in molecular dynamics (MD) simulation. In this letter, the applicability of three types of average kinetic energy as measures of temperature is investigated, i.e., the total kinetic energy, kinetic energy without the centroid translation part, and thermal disturbance kinetic energy. Our MD simulations indicate that definitions of temperature based on the kinetic energy including rigid translational or rotational motion may yield unrealistic results. In contrast, the thermal disturbance kinetic energy has wider applicability to temperature computation in non-equilibrium molecular dynamics simulation. If small samples need to be used for local temperature, then a calibration approach is proposed to eliminate the sample-size dependence of the average disturbance kinetic energy.