The band structure and Fermi surface of calcium

The conduction bands for Ca have been computed with a Slater-type potential and it is found that for less than 20% or more than 75% of the exchange term there is no overlap between the first and second band. The conduction and core bands, density of states, Fermi energy and Fermi surface are computed for an optimum value of the exchange. It is found that the Fermi surface is connected and agreement with all the known results of the de Haas-van Alphen effect is obtained. Although this is in apparent disagreement with the results of Vasvári et al. who obtain an unconnected Fermi surface, their Fermi level was wrongly located and when the error is corrected a connected surface should almost certainly be obtained. The effect of pressure on the Fermi surface and conductivity of Ca is discussed.