Actinides

Abstract

For Ac and Th the total energy graphs correctly predict the fcc structure as the ground state. The best agreement with experiment for the equilibrium lattice parameter corresponds to LDA calculations for Ac and GGA results for Th. From the energy bands and DOS in these two elements we show the f-bands to lie above the Fermi level (about 0.5 Ry for Ac and 0.2 Ry for Th). In addition, for Ac and Th we present TB parameters in an spd Hamiltonian by omitting the f-bands. For the rest of the elements in this row (Pa to Md) we found that the Fermi level starts entering the f-bands in Pa and gradually the f-DOS at E_F becomes very large reaching a maximum at the element Californium and the starts decreasing until the Fermi level moves above the f-bands in Nobelium. Comparing with the lanthanides we see that the f-bands are much wider in the actinides. However, as in the lanthanides standard density functional theory fails to give a total energy minimum in the elements Pa to Md and therefore we assumed the fcc structure and we present only the energy bands and DOS. For No and Lr for which the f-bands are away from E_F and do not hybridize with d-bands, it was possible to do an energy minimization for the fcc and bcc lattices.