EAM Potentials for Characterisation of HCP Nuclear Materials

Abstract

AbstractMolecular dynamics (MD)-based simulations to study material behaviour are based on the classical mechanic approach. In recent times, molecular dynamics has emerged as a vigorous technique to study metals for their structure and behaviour. MD is a semi empirically computer modelling technique based on Newton’s second law of motion for an N-body system. The atoms are treated as classical particles and the interaction and time evolution of a system of particles is mapped by solving for their potential energy using semi empirically derived interatomic potential. The position, velocity and acceleration of each atom in space are further calculated by Newton’s second law of motion at every integration time step. The predictive power of the simulation depends on the reliability of the interatomic potential. The parameters of the potential function are derived by fitting to known experimental properties such as lattice constants and elastic constants. MD simulations can be employed to study atomistic phenomena occurring at small timescales of picoseconds and femtoseconds. When compared to first principle simulations which can only handle a few thousand atoms and small simulation cells, MD-based simulations can handle millions of atoms. This makes MD-based simulations a great option to study phenomena like radiation damage and defect generation in nuclear materials. HCP materials like Zr and Ti are widely accepted as nuclear materials. In order to study irradiation defects in such materials, it is imperative to take caution to use interatomic potential which can correctly reproduce point defect formation and migration energies. The anisotropy and complex crystal structure of HCP materials make irradiation studies even more challenging. This chapter presents examples of the application of EAM potentials to understand the point defect formation and migration energies and diffusion anisotropy, and presents an assessment of available potentials for studying the radiation response of HCP nuclear materials.KeywordsEAM potentialHCP materialsAnisotropyPoint defectsMolecular DynamicsMigration energyIrradiationDislocation loop