Impact of thermostat on interfacial thermal conductance prediction from non-equilibrium molecular dynamics simulations

The knowledge of interfacial thermal conductance (ITC) is key to understand thermal transport in nanostructures. The non-equilibrium molecular dynamics (NEMD) simulation is a useful tool to calculate the ITC. In this study, we investigate the impact of thermostat on the prediction of the ITC. The Langevin thermostat is found to result in larger ITC than the Nose-Hoover thermostat. In addition, the results from NEMD simulations with the Nose-Hoover thermostat exhibit strong size effect of thermal reservoirs. Detailed spectral heat flux decomposition and modal temperature calculation reveal that the acoustic phonons in hot and cold thermal reservoirs are of smaller temperature difference than optical phonons when using the Nose-Hoover thermostat, while phonons in the Langevin thermostat are of identical temperatures. Such a non-equilibrium state of phonons in the case of the Nose-Hoover thermostat reduces the heat flux of low-to-middle-frequency phonons. We also discuss how enlarging the reservoirs or adding an epitaxial rough wall to the reservoirs affects the predicted ITC, and find that these attempts could help to thermalize the phonons, but still underestimate the heat flux from low-frequency phonons.