Thermodynamic Functions and Molecular Structure of Glass-forming Liquid

Abstract

In cooperative molecular dynamics, the molecules of the glass-forming liquids are partitioned to sub-molecular units named “beads”. The beads have been empirically defined. Recently, a method for measuring the beads has been suggested. In this method the difference between entropy of the liquid and the crystal, known as excess entropy, has been used. Here, it is found that all other thermodynamic quantities are functions of the number of beads in the molecules, and their number can be measured from each of them. A subject of special interest is to measure the number of beads from the difference in the heat capacity between the liquid and the crystal, and the liquid and the glass as the configuration and the vibrational components in the number of the beads, can be separated. In Adam–Gibbs, post Adam–Gibbs theories as well as the potential energy landscape paradigm the thermodynamic nature of the dynamical phenomena is being studied. From the obtained equations, transition in the opposite direction became possible, namely the thermodynamic functions can be estimated from the dynamic experiments, if the number of the beads in the molecules are known. The theory is examined from the experimental results of 3-bromopentane.