First-principles investigation of the relation between structural and NMR parameters in vitreous GeO2

NMR parameters of 73Ge and 17O in vitreous GeO2 and quartz GeO2, including the isotropic shifts, the quadrupole coupling constants CQ, and the electric-field-gradient asymmetry parameters η, are determined through density functional calculations. Clear correlations are established between 73Ge shifts and the mean of the four neighboring Ge-O-Ge bond angles, and between CQ and η parameters of 17O 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 deg. 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.