FRUSTRATION-LIMITED CLUSTERS IN LIQUIDS

We present a continuum theory of frustration-limited clusters in one-c omponent glass-forming liquids that accounts, in part, for the recentl y reported [Fischer et al., J. Non-Cryst. Solids, 131-133, 134 (1991)] , and quite unexpected, presence in simple glass-forming liquids of st able clusters at low temperatures (T) and the even less expected persi stence for very long times of these clusters at higher Ts. The model i s based on the idea that there is B local structure that is energetica lly preferred over simple crystalline packing, which is strained (frus trated) over large distances; although in a curved space the preferred packing could lead to ''ideal'' crystallization at temperatures that are usually above the actual freezing temperature, in ''flat'' space t his transition is narrowly avoided. We are led to a new ansatz for the T dependence of the viscosity, which permits us to collapse data for many liquids onto a universal curve.