Electric field gradient for nontransitional dilute alloys of aluminium

The electric field gradient (q) and asymmetry parameter (η) are calculated for nontransitional dilute alloys of Al. The nonlocal model potential is used to evaluate the valence-effect contribution and the elastic continuum model is adopted to evaluate the size-effect contribution. Although the nonlocality of the model potential greatly modifies the valence-effect contribution, the valence effect alone does not explain the observed values of q and η. The size-effect contribution is found to be larger than the valence-effect contribution. The calculated and experimental values of q and η are found to be in close agreement for almost all the alloys, and these are found to be correlated to the magnitudes of effective charges on impurities. A comparison of q and η for Cu and Al alloys is also presented.