Total Energy as a Function of Lattice Parameter for Copper via the Self-Consistent Augmented-Plane-Wave Method

Abstract

The $X\ensuremath{\alpha}$ exchange approximation was used in self-consistent augmented-plane-wave calculations on metallic copper. The value assigned to $\ensuremath{\alpha}$ (0.7225) was chosen to yield zero pressure at the experimentally determined lattice spacing, and the calculations were carried out for six different lattice parameters. The total energy as a function of lattice parameter, resulting from these calculations, was used to determine pressure as a function of lattice parameter, cohesive energy, and compressibility. The cohesive-energy calculation gave 0.286 Ry, which is within 11% of the experimental value of 0.257 Ry. The compressibility, as calculated for two sets of calculated pressure as a function of lattice parameter, was found to agree with the experimental value to within 7% for one set of pressures and to within 4% for the other.