Electronic band structure of h. c. p. electron phases based on the noble metals

Abstract

Measurements of the electronic specific heat coefficient and of the limiting Debye temperature are reported for several close-packed hexagonal intermediate phases in the systems Cu-Ge, Ag-Sn and Ag-Cd. The obtained results, together with previous similar work, conform to a general pattern which suggests that the electronic structure of all h. c. p. phases based on the noble metals can be described in terms of a common nearly rigid band for the conduction electrons. The details of the trend in the density of states are similar to the calculated density of states trends for the h. c. p. metals Zn and Be. The main feature is a large peak in the range of electron concentration between 1.4 and 1.8 which is most likely the result of Fermi surface contacts with the {10.1} Brillouin zone planes, and overlaps across the {10.0} zone planes. A secondary feature is the onset of overlaps across the {00.2} zone planes. A model of an inscribed Fermi sphere into the Brillouin zone is sufficient to indicate the expected behaviour of the trend in the electronic heat capacities in individual phases. Electron-phonon enhancement in the h. c. p. phases appears to be a nearly constant factor, amounting to about 30% of the measured electronic heat capacity values.