Molecular dynamic simulation of grain boundary diffusivities and vacancy behavior in Al

The embedded atom method (EAM), where a highly accurate empirical inter-atomic potential calculation is possible in comparison with the two-body pair potential, is used for the molecular dynamics (MD) simulation. Parameters are fitted for Al and Cu so as to reproduce the metal properties such as elastic constants (C11, C12, and C44) and single vacancy formation energy. Micro-void motion in an Al crystal is simulated using the MD simulator for the EAM and the Morse potentials. The velocity of the micro-void under the EAM potential is less than that under the Morse potential. This discrepancy results from the difference in the surface adsorption energies of these potentials. To compare the accuracy of the Morse and the EAM potentials, surface adsorption energies are calculated. The calculated surface adsorption energy for EAM potential was 90% of the ab initio calculation and the one for the Morse potential was 16%, which implies accuracy of the EAM’s energy evaluation is higher than that of the Morse potential. The grain boundary diffusion for Al has been characterized by using the MD simulation with the EAM potential. Diffusivity and activation energy for several grain boundaries are calculated for several conditions. These simulation results are effective to find a way to improve the electromigration failure.