Calculation of the Band Structure for Copper as a Function of Lattice Spacing

Calculations are described which relate to the change in the electronic band structure of copper with change in lattice spacing. The calculations were performed using previously described constant-energy search techniques based on the Korringa-Kohn-Rostoker method for band-theory calculations. Included in the results are a total of 26 066 points on each of three Fermi surfaces corresponding to lattice spacings $a$, $0.995a$, and $0.99a$, with $a$ being the normal lattice constant of copper. Using the measured value for the volume compressibility, our results give calculated changes in the Fermi surface with pressure which agree very well with recent de Haas-van Alphen experimental results. The calculated results are also consistent with the pressure dependence of reflectivity measurements, and with experiments thermodynamically related to the pressure dependence of the density of states at the Fermi energy. These results are based on band structures obtained from potentials calculated by a commonly invoked prescription using free-atom charge densities and Slater exchange. When considering the uncompressed metal, this prescription has been found to generate potentials giving widely varying band structures when different free-atom charge densities are used. However, once free-atom charge densities have been found which generate a reasonably accurate potential for the uncompressed metal, we conclude from the present results that the potential prescription appears to be very promising in its ability to accurately describe changes in metallic band structures with changes in lattice spacing.