Role of Magnesium in Soda-Lime Glasses: Insight into Structural, Transport, and Mechanical Properties through Computer Simulations

The role of Mg in soda-lime glasses was elucidated by classical molecular dynamics (MD) simulations. The effect of the replacement of CaO for MgO on the structure, transport, and elastic properties of a series of glasses with compositions 15Na2O·(10 − x)CaO·xMgO·75SiO2 (x = 0, 5, and 10 mol) was studied. Different structural roles were found for the Ca and Mg ions. The former, coordinated by six oxygen atoms, acts as a network modifier, while the latter, four-fold coordinated, participates in the silica network. Consequently, Na ion diffusion is favored by the replacement of MgO for CaO in these glasses, as shown by variation in the computed diffusion coefficients and activation energy of the process in the series of glasses studied. Moreover, the consequences of these structural modifications on the elastic properties (Young’s modulus, shear modulus, bulk modulus, Poisson’s ratio, and compressibility) of the glasses were evaluated by means of energy minimization techniques carried out on the structures obtained by MD simulations.