Electronic structure of rare-earth orthovanadates and its relation to photoelectron and optical spectra

The electronic structure of some rare-earth orthovanadates, RVO4, where R=La,Ce,Nd,Eu,Tb,Dy,orYb, has been studied using the discrete variational X method. Charge and spin densities and the derived potentials for clusters embedded in the crystal lattice were iterated to self-consistency with the use of the self-consistent charge procedure. The results are compared with experimental x-ray photoelectron spectra (XPS) and atomic calculations. Eigenvalues (or transition-state energies) are compared with XPS binding energies and the calculated exchange splittings of lanthanide 4s, 5s, and 4f levels are compared with experiment. For 4f's, the exchange splitting between the least-bound spin-up and spin-down states is measured. An analysis of optical and luminescent properties is made based on the cluster calculations. The results show that the lanthanide 4f orbitals play an active role in bonding, and that luminescence can be related to a resonant energy transfer from excited vanadate orbitals to the lanthanide 4f states.