On the nature of unique boron sites in borate glasses

The ¹¹B NMR spectra of borate glasses can be accurately computer-simulated using a simple model for the electric field gradient at a boron site in the BO₃ and BO₄ structural units, assuming these structural units are relatively undistorted. Deviations from the average OBO bond angle in these two sites are determined from the simulations to be less than ± 2° in borate glasses. There is no evidence for increasing distortion in the fundamental structural units with increasing metal oxide content.