Effect of the f-Orbital Delocalization on the Ligand-Field Splitting Energies in Lanthanide-Containing Elpasolites

摘要

The ligand-field induced splitting energies of f-levels in lanthanide-containing elpasolites are derived using the first-principles universal orbital-free embedding formalism [Wesolowski and Warshel,J.Phys.Chem.1993,97,8050].In our previous work concerning chloroelpasolite lattice (Cs_2NaLnCI_6),embedded orbitals and their energies were obtained using an additional assumption concerning the localization of embedded orbitals on preselected atoms leading to rather good ligand-field parameters.In this work,the validity of the localization assumption is examined by lifting it.In variational calculations,each component of the total electron density (this of the cation and that of the ligands) spreads over the whole system.It is found that the corresponding electron densities remain localized around the cation and the ligands,respectively.The calculated splitting energies of f-orbitals in chloroelpasolites are not affected noticeably in the whole lanthanide series.The same computational procedure is used also for other elpasolite lattices (Cs_2NaLnX_6,where X=F,Br,and I)-materials which have not been fabricated or for which the ligand-field splitting parameters are not available.