Molecular study on anisotropic thermal conductivity of nanoscale liquid argon films with different configurations

Abstract

The thermodynamic and transport properties of thin films may be substantially divergent from their bulk materials. This is especially distinguished for nanoscale liquid films, as demonstrated by prior work about the specific heat capacity of nanoscale water films. Furthermore, the forms of thin liquid films, either freestanding, sessile or confined, also exhibit apparent impact on the properties. In this investigation, the influence of size and solid/liquid interface on the thermal conductivities of nanoscale liquid argon films with these different forms is studied by employing the molecular dynamics method. The results show that the anisotropy of the thermal conductivity is closely related to the configuration, but weakened while the film thickness increases. The relationships between the anisotropic thermal conductivities and the thin film size are revealed by considering the contribution of a solid/liquid interface to the thermal conductivity. The reason is analyzed in the aspect of size and interface by comparison of the densities, potential energy distributions, and vibrational densities of state of argon atoms, which show asymmetry in the directions parallel and perpendicular to the sessile film. Thus, insight is provided into the interface effect on the anisotropic thermal conductivity of nanoscale liquid argon films with different forms which can be found in many applications including interface separation, evaporation, and distillation.