The impact of the thermostats on the non-equilibrium computer simulations of the interfacial thermal conductance

Abstract

Non-equilibrium molecular dynamics simulations have expanded our ability to investigate interfacial thermal transport and quantify the interfacial thermal conductance (ITC) across solid and fluid interfaces. NEMD studies have highlighted the importance of interfacial degrees of freedom and the need to include effects beyond traditional theoretical methods that rely on bulk properties. NEMD simulations often use explicit hot and cold thermostats to set up thermal gradients. We analyse here the impact of the thermostat on the calculated ITC of the gold-water interface. We employ a polarisable model for gold based on Drude oscillators. We show that the 'local' Langevin thermostat modifies the vibrational density of states of the polarisable solid, resulting in ITCs that depend very strongly on the damping constant of the thermostat. We report an increase of the ITC of up to 40% for short damping times. Damping times longer than the characteristic heat flux relaxation time of the solid lead to converging ITCs. In contrast, the ITCs obtained with global canonical velocity rescale thermostats are independent of the damping time but lead to a break of equipartition for Drude particles. Setting individual thermostats for the core and shell sites in the Drude particle solves this problem.

Phonon thermophoresis of crystalline nanoparticles in liquids

“…For example, the phonon effect known as Kapitsa resistance, which decreases the phonon heat conductivity at the solid–solid or solid-quantum liquid boundary (assumed to be relevant for classical liquids in ref. 47), may decrease the effective heat conduction of the particle by no more than twenty percent even at total locking of the phonon particle heat conductivity by the Kapitsa barrier. These observations indicate that mainly the random (diffusive) motion occurs, while thermal elastic waves are only weakly excited.…”

Thermal conductance of the water–gold interface: The impact of the treatment of surface polarization in non-equilibrium molecular simulations

“…The thermostats are set as follows: all the atoms in the gold slab are thermostatted using the Langevin thermostat with a time constant of 2.5 ps (see Ref. 34 for further information on the impact of the thermostat on the ITC). For water, we defined a thermostatting region at a distance of ∼22 Å from the interface.…”