First-principles investigation of the relation between structural and NMR parameters in vitreous GeO2
NMR parameters of Ge-73 and O-17 in vitreous GeO2 and quartz GeO2, including the isotropic shifts, the quadrupole coupling constants C-Q, and the electric-field-gradient asymmetry parameters., are determined through density functional calculations. Clear correlations are established between Ge-73 shifts and the mean of the four neighboring Ge-O-Ge bond angles, and between CQ and. parameters of O-17 and the local Ge-O-Ge angle. Available experimental data for CQ and the corresponding established correlation are used to extract the value of 135 degrees for the average Ge-O-Ge angle in vitreous GeO2. The features of the Ge-O-Ge bond angle distribution of vitreous GeO2 derived in this work are consistent with those inferred from other experimental probes.