Vibrational and configurational parts of the specific heat at glass formation

This is the authors' abstract. We don't add key points for this paper.

The specific heat Cₚ of a liquid is partly vibrational, arising from change in phonons and anharmonic forces with temperature T, and partly configurational, arising from change in the structure with T. The first determines a liquid's elastic resistance to stress or rigidity and the second its fluid behavior. Both are thought to decrease on liquid's vitrification, and their ad hoc estimates are currently used for understanding a supercooled liquid's dynamics. We report measurements of the vibrational part, Cp,vib, and determine the configurational part. It is found that there is almost no decrease in Cp,vib on structural freezing of the polymer melts, and the decrease in Cₚ is configurational. An interpretation of the finding is that the curvature of the fixed configurational energy minimum in which a polymer glass structure is trapped and the associated anharmonicity have quantitatively the same effect on Cₚ as the corresponding two sources when its melt explores a multiplicity of high energy minima and its volume changes.