Molecular dynamics methods (periodic boundary conditions), and a many-body potential, were used to calculate the formation energies of mono-vacancies, di-vacancies, tri-vacancies and tetra-vacancies with various configurations. The energetically favorable configurations for small vacancy clusters were deduced. The activation energies for mono-vacancy migration were also estimated, and the effect of a vacancy cluster upon the migration of neighboring vacancies was analyzed.

The Stable Configurations of Small Vacancy Clusters in Ni3Al. Hu, S., Wang, T., Li, Y.: Modelling and Simulation in Materials Science and Engineering, 1996, 4[5], 493-9