Vibrational and configurational parts of the specific heat at glass formation
Anno: 2008
Autori: Tombari E., Ferrari C., Salvetti G., Johari G.P.
Affiliazione autori: 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 C-p 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, C-p,C-vib, and determine the configurational part. It is found that there is almost no decrease in C-p,C-vib on structural freezing of the polymer melts, and the decrease in C-p 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 C-p as the corresponding two sources when its melt explores a multiplicity of high energy minima and its volume changes.
Giornale/Rivista: PHYSICAL REVIEW B
Volume: 77 (2) Da Pagina: 024304 A: 024304
Parole chiavi: DIFFERENTIAL SCANNING CALORIMETRY; NARAYANASWAMY-MOYNIHAN MODEL; DOI: 10.1103/PhysRevB.77.024304Citazioni: 19dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2024-04-14Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui