Modeling of the structure of sodium borosilicate glasses using pair potentials

Structural models of sodium borosilicate glasses were prepared by means of molecular dynamics (MD) technique using pair potentials over a wide compositional range. The local structures around B, O, and Si obtained from the structural models were compared with experimental (11)B NMR, (17)O NMR, and (29)Si NMR data. It was found that atomic arrangements of B, O, and Si in the structural models were similar to the experimental results indicating that the simulations can reproduce the chemical bonds of the real glasses. These results confirm that even if the MD technique using the pair potentials is quite simple, it is enough to capture the essence of the amorphous materials. In the linkage of the cation-oxygen polyhedra, the differences were observed between the structural models and the experimental results. The factors responsible for these differences are discussed with respect to the equilibrium reactions between the cation-oxygen polyhedra at a higher temperature. The discussion suggests that the differences were caused by the extremely higher quenching rate than the real glasses as well as by the simplicity of our pair potential and the smaller size of the unit cell.