Density-functional theory based molecular dynamics simulation of tetrahedrite thermoelectrics: Effect of cell size and basis sets

Abstract

In this work we investigated the effect of cell size and basis sets on the structural and dynamic properties from density-functional theory based molecular dynamics simulations. Three simulations, 1 × 1 × 1 cell with plane wave (PW) basis set, 1 × 1 × 1 cell with atomic orbital (AO) basis, and 2 × 2 × 2 cell with AO basis, were performed at 300 K on a model material: tetrahedrite thermoelectric Cu10Zn2Sb4S13. It was found that lattice parameters, vibrational spectra, heat capacity, and EXAFS spectra are comparable for three simulations. In addition, the 2 × 2 × 2 cell can provide access to length scales closer to the hydrodynamic limit, which allow us to identify the sound/acoustic modes in momentum/velocity correlation, as well as quasi-localized modes that are possibly responsible for its low lattice thermal conductivity.