Pressure Studies in Copper. Part I. Preliminary Calculations on the Effect of Pressure on the Electronic Band Structure

摘要

For strains confined to the elastic region the electronic energy changes produced will be small and a perturbation approach would appear to be best. A perturbation approach for this problem is developed for hydrostatic strain. Two sets of preliminary calculations are described which indicate that the Modified Plane Wave perturbation program is precise to within about 0.0005 to 0.001 Ry. These calculations show that energy shifts due to 'potential' effects and to 'geometric' effects are of the same order of magnitude and can be like or oppositely directed. Results are compared with reflectance measurements. A scale-change procedure which recasts the perturbation problem is described and is shown to give results consistent with the straightforward perturbation approach to within about 0.0005 Ry in most cases. Brief comments on symmetry changes under uniaxial strain are given. (Author)