Electronic structure of lithium tetraborate Li2B4O7 crystals. Cluster calculations and x-ray photoelectron spectroscopy

The results of an investigation of the electronic structure of lithium tetr aborate crystals using experimental (x-ray photoelectron spectroscopy! and theoretical (quantum-chemical modeling) methods are reported. The experimen tal spectrum of the valence-band states of the crystal lies 2-15 eV below t he Fermi level and is due primarily to boron-oxygen groups (B4O9). The quan tum-chemical calculations were performed self-consistently, using the stand ard variant of the scattered-wave method in the model of a cluster embedded in a lattice of point charges. The data obtained on the partial contributi on of the model densities to the one-electron spectrum of the [B4O9](6) clu ster make it possible to interpret the fine structure of the experimental s pectrum of the valence-band states. (C) 1999 American Institute of Physics. [S1063-7834(99)01401-X].