Keywords:glass transition, supercooled liquids, molecular dynamics simulations
We perform molecular dynamics simulations for a silica glass former model proposed over a wide range of densities. The density variation can be mapped onto the change of the potential depth between Si and O interactions of this model. By reducing the potential depth (or increasing the density), the anisotropic tetrahedral network structure transforms into the isotropic structure with the purely repulsive soft-sphere potential. Correspondingly, the temperature dependence of the relaxation time exhibits the crossover from Arrhenius to super-Arrhenius behavior. Being able to control the fragility over a wide range by tuning the potential of a single model system helps us to bridge the gap between the network and isotropic glass formers and to obtain the insight into the underlying mechanism of the fragility.