Electronic states of lanthanides in the ternary thiogallate CaGa 2 S 4 in view of relativistic first principle calculation

Abstract

The electronic states of lanthanide (Ln) atoms doped into the ternary thiogallate CaGa2S4 are investigated from the relativistic first principle calculations by the discrete variational Xα method (relativistic DV-Xα) on LnCa8Ga12S24 spherical clusters. In view of the self-consistent charge (SCC) convergence, atomic coordinates in the cluster are optimized. As the result, a certain lattice contraction is locally induced around the LnCa substitution by more than 30% in maximum. The 4f orbitals of the Ln atom are not electronically isolated but form many molecular orbitals mainly hybridized with valence orbitals of the surrounding S and the second nearest Ga atoms. The LS coupling of the 4f orbitals does not always result in the discrete level splitting as the j = 5/2 and 7/2 states. Both of these states are partially degenerated to make some molecular orbitals. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)