Ab initio calculation of electromigration effects at polyvacancy clusters in aluminum

The driving force on a migrating atom at polyvacancy clusters in aluminum is calculated using an ab initio multiple-scattering Green’s function method. The open structure of polyvacancy clusters is considered as a model to simulate electromigration over a surface and as a start to simulate electromigration along a grain boundary. A random isotropic distribution of vacancies tends to decrease the driving force. In a configuration which resembles an atom on a surface the decreasing tendency is reinforced. In a configuration which resembles the situation at a grain boundary more specificly the vacancies are concentrated on the line along which an atom migrates. For such a configuration the force tends to increase.