An interaction potential to study the thermal structure evolution of a thermoelectric material: β-Cu2 Se.

Abstract

An interaction potential model has been developed, for the first time, for β-Cu2 Se using the ab initio derived data. The structure and elastic constants of β-Cu2 Se using the derived force-field are within a few percent of DFT derived structure and elastic constants and reported experimental structure. The derived force-field also shows remarkable ability to reproduce temperature dependent behavior of the specific heat and thermal expansion coefficient. The thermal structure evolution of the β-Cu2 Se is studied by performing the molecular dynamic simulations using the derived force-field. The simulation results demonstrate that the Cu ions moves around the equilibrium lattice position within the temperature range of 500-800 K. However, at a temperature > 800 K, the Cu ions starts diffusing within the material, while the Se ions remains in their lattice position. The evaluated thermodynamic properties such as free energy and excess entropy, show that the increased Cu-Se interaction with the temperature makes the system more thermodynamically stable. © 2017 Wiley Periodicals, Inc.