A unified 23Na NMR chemical shift correlation with structural parameters in multicomponent silicate-based glasses

From a large ensemble of 34 silicate-based glasses from the borosilicate, phosphosilicate, and borophosphosilicate systems that comprise either Na as a sole glass-network modifier or when mixed with Ca, we established a good correlation between the ²³Na average isotropic chemical shift () and the average coordination number of Na and the mean Na–O distance. The latter parameters were obtained by atomistic molecular dynamics simulations. We also demonstrated that is essentially independent on the precise network forming (Si, B, P) species but depends primarily on the net molar fraction of Na and Ca, thereby offering a straightforward ²³Na chemical shift prediction from the glass composition alone.