QUASI-PARTICLE LIFETIMES EFFECTS ON DEVIATIONS FROM VEGARDS RULE IN AG-PD DISORDERED ALLOYS

The deviations from linearity in the concentration dependence of latti ce spacings in AgcPd1 - c have been recently related to the topology c hanges shown by the Fermi Surface, or Electronic Topological Transitio ns (ETTs), of this alloy. Using an extension of the ETTs theory to fin ite-temperature and impurity scattering case, and in terms of a simple Rigid Band Model, we study such deviations and interpret them as the results of the filling of the hole pocket centered at the X point of t he Brillouin Zone, remarking the role of the finiteness of the quasi-p article lifetime of the relevant states. We also show how ab initio ca lculations based on the Coherent Potential Approximation underestimate these lifetimes.