Assessment of transition-metal coordination in glasses by electron energy-loss spectroscopy

In a combined experimental and theoretical study, it is shown that electronic structure calculations in the local density approximation on adequately sized model clusters unequivocally explain the Ti-L2,3 electron energy-loss near-edge structure (ELNES) of pentahedrally coordinated Ti⁴⁺ in the fresnoite framework structure-type compound Ba₂TiSi₂O₈. Based on an in-depth discussion of the electronic structure-ELNES relationship in crystalline matter, the highly resolved Ti-L2,3 ELNES of amorphous Ba₂TiSi₂O₈ (2BaO-TiO₂-2SiO₂ glass) is interpreted in terms of Ti⁴⁺ coordination in the glass. The results demonstrate that high-resolution ELNES spectroscopy is a promising and powerful technique for atomistic-structure studies of amorphous matter.