ELECTROMIGRATION IN TRANSITION-METALS .3. SUBSTITUTIONAL IMPURITIES IN CU, AG, AL AND NB

Using the KKR Green function method, the electromigration wind valences of several substitutional impurities in Al and in the transition metals Cu, Ag and Nb have been calculated. In a complete migration jump the migrating ion exchanges position with a neighbouring vacancy. The present study is limited to the initial position in such a migration jump and to points along the migration path near to it. The complete band structure as well as all multiple scattering effects for the impurity cluster embedded in a crystal have been accounted for. For self-electromigration in Cu, Ag and Nb a positive wind valence is calculated while in Al the wind valence is negative. Sb in Ag has a large negative wind valence at the initial position. The constructed potentials for Cr and Fe in Nb yield negative wind valences for the impurities. It is concluded that the saddle-point configuration, where the impurity is midway along the path, generally will provide a large contribution to the average wind valence along the path.