Strong to fragile transition in a model of liquid silica

The transport properties of an ionic model for liquid silica [1] 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. Département de Physique des Matériaux (UMR CNRS 5586), Université Claude Bernard, 43 bd. du 11 novembre 1918, F-69622 Villeurbanne Cedex, FRANCE Laboratoire de Sciences de la Terre (URA 726), Ecole Normale Supérieure de Lyon, 46 Allée d’Italie F-69364 Lyon Cedex 07, FRANCE Laboratoire de Sciences de la Terre (URA 726), Institut Universitaire de France, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07, FRANCE