Résumé
In this work we present the structural properties of lithium tetrasilicate glass (LS4) obtained by combined classical and Car-Parrinello molecular dynamics simulations. The computed features are compared with corresponding experimental results as well as to those obtained for sodium tetrasilicate glass (NS4) models generated using the same approach, and containing the some percentage of alkali oxide. The ab initio description improves the comparison of the structural characteristics with experimental data, in particular concerning the Li-O, Si-Li and Si-Si bond lengths. The influence of the network modifier nature on the relevant structural parameters is further examined in terms of their correlations to the first-principles calculated NMR parameters of our glassy models. For both glasses, 29Si MAS NMR measurements are reported and the obtained experimental spectra are compared to the theoretical ones.