Nature of long-range correlations of density fluctuations in glass-forming liquids.

Abstract

Based on a concise review of the experimental data, a theory of the structural, kinetic, and dynamic features of the Fischer cluster is put forward. This theory is based on the idea of heterophase fluctuations of glass-forming liquids. According to these ideas in a one-component liquid the solidlike and fluidlike transient associations of molecules (fluctuons) are formed. The fluctuons differ in the short-range order and, consequently, in the free energy. They form a random free energy landscape. The random field free energy functional of the Ginzburg-Landau type, which accounts for the free energy landscape, is deduced. Based on this, the phase equilibrium, critical behavior, and ordering phenomena of the heterophase liquid are considered. It is shown that in the critical region an effective attractive interaction of the fluctuons results in their gravitation and formation of correlated fractal aggregations. The aggregation consists of the fluctuons of similar short-range order. The fractal aggregation formation is a special structural state of the liquid above the glass transition temperature. The condition at which the aggregations are formed is formulated. Thus it is shown that the Fischer cluster is an array of fractal aggregations of fluctuons. The growth kinetics and dynamics of the Fischer cluster are described. The experimental data are analyzed and discussed using the theory that is put forward.