Configurational specific heat of molecular liquids by modulated calorimetry
Authors: Tombari E., Ferrari C., Johari G.P.
Autors Affiliation: Istituto per i Processi Chimico-Fisici Del CNR, via G. Moruzzi 1, 56124 Pisa, Italy; Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada
Abstract: The specific heat of a liquid varies as its structure and molecular vibrational frequencies vary with the temperature. We report the magnitude of the structural or configurational part C-p,C-conf for five molecular liquids by measuring their dynamic and the apparent specific heats, and find that the unrelaxed or vibrational specific heat, of the equilibrium liquid, is not greatly different from that of the nonequilibrium glass. Therefore, the vibrational part of the specific heat C-p,C-vib does not change substantially when a glass becomes an ultraviscous liquid. This contradicts the inference that there is a large sigmoid-shape (discontinuous) increase in C-p,C-vib as the structure of a glass kinetically unfreezes on heating above its T-g, and further that C-p,C-conf is 20%-50% of the net C-p change at the glass transition.
Journal/Review: JOURNAL OF CHEMICAL PHYSICS
Volume: 129 (5) Pages from: 054501-1 to: 054501-7
More Information: – This research was partly supported by a NSERC’s Discovery Research Grant to one of the authors (G.P.J.), who also acknowledges the hospitality of the IPCF, Pisa, during the period of this study.KeyWords: DIFFERENTIAL SCANNING CALORIMETRY; NARAYANASWAMY-MOYNIHAN MODEL; SUPERCOOLED LIQUID; ENERGY LANDSCAPE; DIELECTRIC-RELAXATIONDOI: 10.1063/1.2961024Citations: 17data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2023-05-28References taken from IsiWeb of Knowledge: (subscribers only)