Variations in the thermal conductivity of insulating thin films with temperature and pressure

The thermal conductivity of a solid thin film was investigated by using two nonequilibrium molecular dynamics (NEMD) methods and changing the calculation conditions. Solid argon was selected as a target material because it has a typical Lennard-Jones (L-J) potential; hence, there was no need to consider the contribution by free electrons to a thermal conductivity. The results were not influenced by the adopted NEMD method, and there were no appreciable effects due to changes in the calculation conditions. The thermal conductivities calculated by using the MD simulations were compared with the available experimental data obtained from the bulk state, and the system's temperature and internal stress were confirmed to affect the thermal conductivity. From our investigation, the internal stress is explicitly an important factor that influences the thermal conductivity of solids; a micro-scale system has a lower thermal conductivity than the bulk material does. The temperature dependence was also carefully investigated, and good qualitative agreement with existing experimental data was obtained.