GRAIN-SIZE-DEPENDENT THERMAL CONDUCTIVITY OF POLYCRYSTALLINE ARGON BY MOLECULAR DAYNAMICS SIMULATION

摘要

The thermal conductivity of polycrystalline solid argon is investigated by molecular dynamics simulation. Three-dimensional Voronoi tessellation technology is employed to generate periodic polycrystalline structures consisting of randomly-shaped grains with controlled size. The Green-Kubo method is then used to calculate the thermal conductivity according to the fluctuation-dissipation theorem. The constructed polycrystalline is relaxed long enough in all the simulations. Random-grain polycrystalline configurations with the same average grain size are generated and the randomicity effect on thermal conductivity is found less than 15%. Configurations of polycrystalline argon with average grain size from 2.5 nm to 15.0 nm are then generated to obtain the relationship between thermal conductivity and grain size. With the average grain size from 2.5 nm to 15.0 nm, the thermal conductivity increases, approaching the thermal conductivity of the bulk crystal. The grain boundary thermal resistance and the limitation on the effective mean free path by grain size are the two important parameters dominating the polycrystalline thermal conductivity.