Electron momentum density in disordered muffin-tinCu1−xNixin the average-t-matrix approximation

In an earlier article we discussed the formalism for evaluating the average electron-momentum density in a random binary alloy by using the average-$t$-matrix approximation to treat the disorder and muffin-tin potentials to represent the constituent atoms. The present paper considers the application of this formalism to ${\mathrm{Cu}}_{1-x}{\mathrm{Ni}}_x$ over a range of alloy compositions. The characteristic effects of disorder on the spectral momentum density $〈\rho (\overrightarrow{\mathrm{p}},E)〉$ are delineated. In discussing the momentum density $〈\rho \left(\overrightarrow{\mathrm{p}}\right)〉$ we focus on how this quantity changes as $x$ increases from 0 to 1 and the Ni $d$ band develops from a virtual bound state below the Fermi energy into a transition-metal $d$ band interacting the Fermi energy. Our detailed predictions in this regard should be amenable to experimental verification by two-dimensional positron-annihilation experiments.