Atomistic modeling of diffusion in the TiAl compound

We combine atomistic modeling methods with kinetic Monte simulations to study self-diffusion in the intermetallic compound L1(0)-TiAl. Atomic interactions in TiAl are modeled with a recently developed embedded-atom potential. The vacancy concentration in TiAl is obtained from a lattice gas model of non-interacting point defects. Molecular dynamics simulations are applied to determine vacancy migration mechanisms in the compound. A set of representative vacancy jumps is identified and their rate constants are computed using the harmonic transition state theory with the reaction path established by the nudged elastic band method. The rate constants are used as input to kinetic Monte Carlo simulations performed at several temperatures and alloy compositions. KMC simulations give us self-diffusion coefficients of Ti and Al, correlation factors and other diffusion characteristics. The results are in reasonable agreement with experimental data. We conclude that our methodology provides a viable approach to diffusion calculations in ordered intermetallic compounds.