Self-consistent relativistic band calculations and the optical conductivities of Ba and Eu

Abstract

The energy band structures for BCC metals Ba and Eu are calculated by the self-consistent symmetrised relativistic APW(SRAPW) method. A one-electron potential is constructed on the basis of the local density approximation. The correlation potential for 4f electrons of Eu is separately treated so as to give the position of the 4f level expected from XPS. Non-relativistic SAPW calculations for Ba and Eu are also carried out for the purpose of comparison. The Fermi surfaces and the extremal cross sections for Ba and Eu are calculated by the SRAPW method and the results are compared with previous theoretical and experimental results. The characteristic features on the Fermi surfaces for Ba and Eu are examined and a remarkable d-like character of the Fermi surface is indicated. The results of the SAPW band calculation is applied for calculations of the optical conductivities within the random phase approximation (RPA) for Ba and Eu in the energy range 0-10.5 eV. The theoretical results are in fairly good agreement with experimental ones. In the case of Eu, it is indicated that the transitions from the 4f states are important to reproduce the experimental results in the region around 7 eV. The effects of self-energy correction on the optical conductivities are phenomenologically considered. It is shown that the different structure observed above 4.5 eV in experiments for Ba and Eu is reasonably explained, if transitions from 4f electrons in Eu are taken into account. This result supports positively the conjecture that the 4f electron levels of Eu locate at the energy region predicted from XPS.