Evidence for Changes ins−dHybridization inα-Phase Cu-Ge Alloys from Positron Annihilation Experiments

Measurements of angular correlation of $\gamma$ rays from positron annihilation in Cu-Ge alloys have been used to reconstruct the momentum density in these alloys in the (110) plane. The densities show, for the first time in a copper alloy, details beyond fermiology which are linked to the detailed character of the electron wave functions and thus to $s-d$ hybridization. This hybridization undergoes large and anisotropic changes upon the alloying of Cu with Ge.