Hydrogen–sodium interdiffusion in borosilicate glasses investigated from first principles

Density functional calculations are performed to investigate the effect of hydronium–sodium interdiffusion in a sodium borosilicate glass. It is found that the substitution of the Na+ network modifiers does not alter the glass covalent network, whereas a bridging bond is systematically broken when the substitution involves Na+ ions bonded to BO4 tetrahedra. The systematic dissociation of hydronium into water and proton suggests that this chemical species probably has a short lifetime in the glass, due to the capability of anionic sites to trap the protons very strongly. The relative basicities of the sites involved are compared, and a nice correlation is found between hydroxyl bond lengths and hydrogen bond strengths present in the hydrated glass.