Energy Band and Fermi Surface of Divalent Metals under Pressure

The energy band structure of face-centered cubic metals Ca, Sr, and Ba was investigated by a pseudopotential-like approximation, using the screened model potential of Abarenkov, Heine, and Animalu. All three of the metals exhibit a negative energy gap at atomospheric pressure, the magnitude of which tends to zero with increasing pressure. According to a symmetry demanded degeneracy along the line WL of the Brillouin zone, the transition to semiconductors with positive energy gap seems to be unlikely. The Fermi surface consists of holes in the first zone around the points $W$ and electrons in the second zone around the points $L$. The dimensions of these surfaces are also decreasing under pressure. The Fermi surface of Ca was studied in detail. Numerical results for the de Haas-van Alphen periods cyclotron masses, are given. The pressure dependence of electrical resistivity of Ca was calculated and found to be in qualitative agreement with the experiments.