  The transport properties of an ionic model for liquid silica at high
temperatures and pressure are investigated using molecular dynamics
simulations. With increasing pressure, a clear change from "strong" to
"fragile" behaviour (according to Angell's classification of glass-forming
liquids) is observed, albeit only on the small viscosity range that can be
explored in MD simulations.. This change is related to structural changes, from
an almost perfect four-fold coordination to an imperfect five or six-fold
coordination. (submitted to "Molecular Simulation")
