Thermal conductivity of diamond and related materials from molecular dynamics simulations

Abstract

Based on the Green–Kubo relation from linear response theory, we calculated the thermal current autocorrelation functions from classical molecular dynamics (MD) simulations. We examined the role of quantum corrections to the classical thermal conduction and concluded that these effects are small for fairly harmonic systems such as diamond. We then used the classical MD to extract thermal conductivities for bulk crystalline systems. We find that (at 300 K) C12 isotopically pure perfect diamond has a thermal conductivity 45% higher than natural (1.1% C13) diamond. This agrees well with experiment, which shows a 40%–50% increase. We find that vacancies dramatically decrease the thermal conductivity, and that it can be described by a reciprocal relation with a scaling as nv−α, with α=0.69±0.11 in agreement with phenomenological theory (α=1/2 to 3/4). Such calculations of thermal conductivity may become important for describing nanoscale devices. As a first step in studying such systems, we examined the mass effects on the thermal conductivity of compound systems, finding that the layered system has a lower conductivity than the uniform system.