Interatomic potentials for atomistic simulations of the Ti-Al system

TL;DR

This paper develops and validates semi-empirical interatomic potentials for the Ti-Al system using the embedded atomic method, enabling accurate atomistic simulations of structural and defect properties at high temperatures.

Contribution

The paper introduces new EAM potentials for Ti-Al that accurately reproduce structural, defect, and thermal properties, improving upon previous models for high-temperature simulations.

Findings

Potentials accurately predict crystal structures and lattice properties.

They describe defect energies, surfaces, and faults reliably.

They show gamma-TiAl is dominated by antisite defects.

Abstract

Semi-empirical interatomic potentials have been developed for Al, alpha-Ti, and gamma-TiAl within the embedded atomic method (EAM) by fitting to a large database of experimental as well as ab-initio data. The ab-initio calculations were performed by the linear augmented plane wave (LAPW) method within the density functional theory to obtain the equations of state for a number of crystal structures of the Ti-Al system. Some of the calculated LAPW energies were used for fitting the potentials while others for examining their quality. The potentials correctly predict the equilibrium crystal structures of the phases and accurately reproduce their basic lattice properties. The potentials are applied to calculate the energies of point defects, surfaces, planar faults in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al system, the proposed potentials provide reasonable description of the lattice thermal expansion, demonstrating their usefulness in the molecular dynamics or Monte Carlo studies at high temperatures. The energy along the tetragonal deformation path (Bain transformation) in gamma-TiAl calculated with the EAM potential is in a fairly good agreement with LAPW calculations. Equilibrium point defect concentrations in gamma-TiAl are studied using the EAM potential. It is found that antisite defects strongly dominate over vacancies at all compositions around stoichiometry, indicating that gamm-TiAl is an antisite disorder compound in agreement with experimental data.