Finite size effects in determination of thermal conductivities: comparing molecular dynamics results with simple models

摘要

The thermal conductivity of nanometric objects or nanostructured materialscan be determined using non equilibrium molecular dynamics (NEMD) simulations.The technique is simple in its principle, and resembles a numerical guarded hotplate experiment. The 'sample' is placed between a hot source and a cold sourceconsisting of thermostatted sets of atoms. The thermal conductivity is obtainedfrom the heat flux crossing the sample and the temperature profile in thesystem. Simulations results, however, exhibit a strong dependence of thethermal conductivity on the sample size. In this paper, we discuss the physicalorigin of this size dependence, by comparing MD results with those obtainedfrom simple models of thermal conductivity based on harmonic theory of solids.A model is proposed to explain the variation of the thermal conductivity withsystem size.