First-principles investigation of the relation between structural and NMR parameters in vitreousGeO2

Abstract

NMR parameters of 73Ge and 17O invitreous GeO2 and quartz GeO2, including the isotropic shifts, the quadrupole coupling constantsCQ, and the electric-field-gradient asymmetry parametersη,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 betweenCQ andη parametersof 17O and the local Ge–O–Ge angle. Available experimental data forCQ and the corresponding established correlation are used to extract the value of135° for the average Ge–O–Geangle in vitreous GeO2. The features of the Ge–O–Ge bond angle distribution of vitreousGeO2 derived in this work are consistent with those inferred from other experimental probes.