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 tetraborate crystals using experimental (x-ray photoelectron spectroscopy) and theoretical (quantum-chemical modeling) methods are reported. The experimental spectrum of the valence-band states of the crystal lies 2–15 eV below the Fermi level and is due primarily to boron-oxygen groups (B4O9). The quantum-chemical calculations were performed self-consistently, using the standard 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 contribution of the model densities to the one-electron spectrum of the [B4O9]6 cluster make it possible to interpret the fine structure of the experimental spectrum of the valence-band states.