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 $\mathrm{Ti}\text{−}{L}_{2,3}$ electron energy-loss near-edge structure (ELNES) of pentahedrally coordinated ${\mathrm{Ti}}^{4+}$ in the fresnoite framework structure-type compound ${\mathrm{Ba}}_2\mathrm{Ti}{\mathrm{Si}}_2{\mathrm{O}}_8$. Based on an in-depth discussion of the electronic structure-ELNES relationship in crystalline matter, the highly resolved $\mathrm{Ti}\text{−}{L}_{2,3}$ ELNES of amorphous ${\mathrm{Ba}}_2\mathrm{Ti}{\mathrm{Si}}_2{\mathrm{O}}_8$ ($2\mathrm{Ba}\mathrm{O}-\mathrm{Ti}{\mathrm{O}}_2\text{−}2\mathrm{Si}{\mathrm{O}}_2$ glass) is interpreted in terms of ${\mathrm{Ti}}^{4+}$ 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.