At present,there have been few direct molecular dynamics simulations on the thermal conductivity of polycrystalline nanofilms.In this paper,we generate polycrystalline argon nanofilms with random grain shape using the three-dimensional Voronoi tessellation method.We calculate the out-of-plane thermal conductivity of a polycrystalline argon nanofilm at different temperatures and film thicknesses by the Muller-Plathe method.The results indicate that the polycrystalline thermal conductivity is lower than that of the bulk single crystal and the single-crystal nanofilm of argon.This can be attributed to the phonon mean-free-path limit imposed by the average grain size as well as the grain boundary thermal resistance due to the existence many grain boundaries in polycrystalline materials.Also,the out-of-plane thermal conductivity of the polycrystalline argon nanofilm is insensitive to temperature and film thickness,and is mainly dominated by the grain size,which is quite different from the case of single-crystal nanofilms.
