The Intermediate Phase in Network Glasses

Michigan State University, East Lansing MI

Investigators

Abstract

0078361 Thorpe This senior and distinguished PI works on properties of glasses but in the framework of a network model. In this view, which focuses on the geometric details such as network connectivity, the network is derived by putting the most important forces in the model to be infinite and the rest are set equal to zero. The resulting model is computationally manageable with a large number of particles. In this model, at a critical (as a function of) average coordination number (generally covalent glasses have large coordination number while the polymeric glasses in general have smaller coordination number), the states evolve in to a rigid and stressed state. However the numerical results show the existence if an intermediate state which is rigid but not stressed. This grant supports further work on this intermediate phase of a network glass. Recent experiments in chalcogenide glasses give preliminary evidence for an intermediate phase of this nature. %%% This senior and distinguished PI is a leader in the broad field of study involving glasses. In particular, guided by his belief that many properties of glasses can be studied using a geometric model, i.e. one made from sticks and balls, he has noticed the presence of curious phase of glass which may have been seen experimentally. Looking at glasses from their dependence on an average coordination number (number of atoms that a given atom may be connected to) there are two phases, one where the glass has a small coordination number, no rigidity and no accumulated stress while at large coordination number, the glass is rigid and it has accumulated stress. Near the transition, and a range of coordination number around the critical value, there is an intermediate phase corresponds to a rigid but unstressed glass. He plans to look at the observable properties of state. ***