Combined 29Si double quantum NMR and MD simulation studies of network connectivities of binary Na2O·SiO2 glasses: new prospects and problems

Quantitative results of structural studies of binary xNa2O·(1−x)SiO2 glasses (x=0.15, 0.20, 0.25), using both experimental (double quantum NMR) and theoretical methods (molecular dynamics simulation), are presented. The primary goal is to verify and quantify connectivities of the various SiO4 species in terms of small clusters of Qn,ijkl units, with n being the number of bridging oxygen atoms of the `centralʹ Q unit. The additional superscripts denote the Q character of the bonded adjacent SiO4 tetrahedra. It is the aim of the paper to compare these DQ NMR results with theoretical predictions by the most recent MD simulations. The current problems and limitations of this new approach are discussed in detail.