Thermal conductivity of thermoelectric material β-Cu2Se: Implications on phonon thermal transport

Thermal transport properties associated with the thermal structure evolution of β-Cu2Se are studied using density functional theory (DFT) and molecular dynamics (MD) simulations. Thermal conductivity of β-Cu2Se is calculated over a temperature range of 400–1000 K using reverse non-equilibrium molecular dynamics simulations. The thermal conductivity found through MD simulations decreases monotonically with increasing temperature, which is in line with the reported experimental data and our calculated DFT data. The average phonon mean free path evaluated using the kinetic theory, found to be within the range of 1.0–1.5 Å, decreases with increasing temperature. Furthermore, we have investigated the temperature-dependent heat transport phenomena using phonon density of states, calculated using MD simulations. The phonon modes are found to shift towards the low frequency numbers with increasing temperature, indicating lower heat carrying capacity of the material and in agreement with the computed thermal conductivity.