Configuration entropy and potential energy landscape in thermodynamics and dynamics of supercooled liquids

Abstract

In thermodynamics of supercooled liquids, sub-molecular units, referred to as “beads,” are used. It has been reported that all thermodynamic functions as well as the parameters in the empirical distribution functions of the potential energy landscape approach appear to be explicit functions of the number of beads in molecules. This finding opens the possibility of measuring the number of beads from each of these functions and estimating the configuration and vibration components in their formation. An enthalpy factor has been introduced and found that within the temperature domain of the invariable enthalpy factor, the molecules partition to a constant number of beads. A correlation has been observed between temperature dependence of the potential barriers, restricting cooperative rearrangement of beads and heat capacity of liquids. Relations connecting the landscape approach with the number of beads in the molecules have been estimated. The molecular equation for configuration entropy obtained can provide guidance for the development of new materials with a desirable configuration entropy. A method for predicting thermodynamic and statistical quantities of supercooled liquids from kinetics is also suggested.