A band theoretical explanation for the electronic specific heat of some copper-gold alloys

Abstract

The low temperature electronic specific heat as a function of Au content in Cu-Au alloys shows interesting features. The specific heat coefficient of disordered alloys lies on a smooth curve below the linearly interpolated elemental metal values. Ordering reduces the value of this coefficient in all cases except that of the CuAu I alloy. It is shown that this behaviour of the electronic specific heat is due to the specific structure of the electronic density of states around the Fermi level. The position and shape of the large dip the authors found at the Fermi level varies with changes in the chemical composition or the crystal structure of the alloy. The singular property of the specific heat of CuAu I can be explained by the lattice contraction in the c direction. Besides these Fermi level properties, the electron density of occupied states, resolved into the total and Au part, is discussed for the case of Cu₃Au I, CuAu I and CuAu₃. Characteristic d-band energies (top, centre and bottom) are also presented. The calculations were performed using the linear-muffin-tin-orbital method.