Development of a genetic algorithm based interatomic potential and application in thermal conductivity study of ThO2 grain boundaries

Abstract

ThO2 is a promising fuel for next-generation reactors due to its superior thermo-physical properties. In this study, we present a Coulomb-Buckingham-Morse interatomic potential for ThO2, developed using a homemade genetic algorithm (GA) method. The potential accurately captures fundamental properties, such as lattice constants, elastic constants, point defect energies, phonon spectra, and thermal conductivity. We apply this potential to perform a systematic study of thermal transport of twenty-one tilt grain boundaries (GBs) in ThO2, which have a significant effect on the macroscopic properties of polycrystalline materials. We demonstrate that the microscopic structure, GB excess energy, and GB disorder index are well correlated with the Kapitza conductance for a wide variety of GBs. Additionally, we discuss the effect of high temperature on the Kapitza conductance, where the GB structure undergoes disordering when approaching the melting temperature, resulting in an increase of thermal resistance. Finally, a detailed analysis of the phonon density of states is presented to reveal the mechanisms of thermal conductance in ThO2.