Modification of Nóse–Hoover Thermostat to Improve Temperature Response in Molecular Simulations

Abstract

This work investigates the modification of the Nóse–Hoover thermostat, a well-known tool for controlling system temperature in nanoscale dynamical simulations. Nóse–Hoover response is characterized by a mean temperature converging to a target temperature. However, oscillations in the actual system temperature consistently appear over time. To reduce these oscillations, the Nóse–Hoover control law is modified to resemble a proportional–derivative controller. The modified thermostat is compared to the standard and shown to significantly reduce deviations. Gains are varied and compared to show effects on response and simulation time. Work–energy calculations show the modified dynamics drive the system to a low-energy state significantly faster than the standard. The behavior of the modified thermostat is illustrated using a simulation of a molten salt solution.