Volume dependence of the electronic structure of lanthanum and cerium

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Abstract
Results of a band structure calculation for the f.c.c. lattices of lanthanum, γ‐and α‐cerium are presented. The computation is based on Altmann's rigorous cellular method. A local potential is used generated according to the standard method. Charge densities of the free atoms are obtained from a SCFXα‐integration of the Dirac equation. Earlier band calculations using the full Slater exchange led to f‐levels far too low in energy. Instead the more adequate Gaspar‐Kohn‐Sham value of 2/3 is used for the exchange scaling factor, which yields reasonable f‐band energies. The Permi level proves to be well below the f‐bands for both metals. As follows from an analysis of the occupied band states in terms of angular momenta, there are f‐admixtures of 0.3 and 0.6 electrons/atom for La and Ce, respectively, which increase slightly under pressure. As the pressure rises the Fermi level moves across three van Hove singularities in the electronic density of states at –15, 10, and at 60 kbar. This is also reflected in topological changes of the Fermi surface which can give rise to isostructural phase transitions. Recent Bremsstrahlung‐ and XPS‐spectra of La and Ce are in fair agreement with the results on the density of states.