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

A kinetic energy-based approach is developed to obtain the correct local temperature of non-equilibrium systems. We have demonstrated that as a temperature measure, the average disturbance kinetic energy of a sample is more applicable than its average total energy, and the latter has been widely used in most molecular dynamics software. However, it is proved and demonstrated by our simulation example that the average disturbance kinetic energy is sample-size dependent. By using a simple equilibrium system as a thermometer, we propose a calibration approach to eliminate this sample-size effect. A vibrating atomic bar is used as an example to test the validity and convergence of various temperature definitions.