Percolative heterogeneous topological constraints and fragility in glass-forming liquids

¹ Department of Civil and Environmental Engineering, Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge, MA, 02139, USA
² Laboratoire de Physique Théorique de la Matière Condensée Université Pierre et Marie Curie Boite 121, 4, Place Jussieu, 75252 Paris Cedex 05, France

Received: 20 November 2013
Accepted: 9 December 2013

Abstract

We present a precise atomic scale approach to topological rigidity theory of sodium silicate glasses and liquids which contain temperature-dependent constraints. Using molecular dynamics simulations, the spatial distribution of such constraints is followed as a function of temperature and pressure. Results show that the distribution of constraints broken by thermal activation is not homogeneous in the system. The spatial extent of these flexible regions shows a percolative behavior at a characteristic temperature which is deeply connected to flexible-to-rigid transitions, and influences the fragility of the glass-forming liquid.