The Fermi surface of dilute copper alloys. II. Theory

Abstract

For pt.I see ibid., vol.5, no.7, p.1307 (1975). A theory is developed to describe the Fermi surface changes in dilute alloys. Following the arguments of Stern, the Fermi energy is considered to be unchanged by alloying and the anisotropic energy shift of the bands is given by the forward part of the T matrix which is then calculated using a muffin tin approximation to describe the alloy. Partial wave analysis gives the Fermi surface changes in terms of anisotropy function and a set of scattering parameters which are conveniently expressed as 'Friedel phase shifts' and which can be determined by fitting the anisotropy of the experimental results. It is shown that the model is closely related to the average T matrix approximation. The observed changes of Fermi surface volume in Cu(Al) and Cu(Ni) alloys are successfully explained and the Friedel sum is also obtained correctly.