Competition for charge compensation in borosilicate glasses: Wide-angle x-ray scattering and molecular dynamics calculations

Wide-angle x-ray scattering (WAXS) has been used to investigate the structu re of complex sodium (alumino) borosilicate glasses containing four, five, and six oxides. WAXS data were compared with previous molecular dynamics ca lculations on these glasses. Small differences were observed which are main ly due to a smaller Si-O distance in the models (1.58 Angstrom) compared to the experimental distance (1.60 Angstrom). These discrepancies were remove d by slightly moving the atomic positions using the reverse Monte Carlo cod e. Changes in the first cation-oxygen distances were sufficient to give an excellent fit of the WAXS data, with little modification of the medium rang e structure. This allows a determination of the structural features observe d in the correlation functions and a validation of the numerical simulation s for complex multicomponent glasses. The dependence of the glass structure on its chemical composition is discussed.