X-ray-absorption near-edge structure of3dtransition elements in tetrahedral coordination: The effect of bond-length variation

The x-ray-absorption near-edge structure (XANES) of transition elements in tetrahedral coordination in crystals and glasses has been studied. We have identified the XANES features in the continuum that can be assigned to multiple scattering within the first coordination shell. The energy positions $E_r$ of the XANES peaks in the continuum follow the rule ($E_r$-$E_b$)$d^2$= const, where $E_b$ is the energy of the prepeak, defined as the first core excitation to the bound antibonding state of $T_2$ symmetry, and d is the interatomic distance. This plot allows us to determine the tetrahedral coordination of a vanadium impurity in a ${\mathrm{SiO}}_2$ glass and to get an estimation of the vanadium-oxygen distance (1.77±0.05 Å).