Endothermic freezing on heating and exothermic melting on cooling

Year: 2005

Authors: Tombari E., Ferrari C., Salvetti G., Johari G.P.

Autors Affiliation: Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche (CNR), via G. Moruzzi 1, 56124 Pisa, Italy; Department of Materials Science and Engineering, McMaster University, Hamilton, Ont. L8S 4L7, Canada

Abstract: Generally, a liquid freezes exothermally on cooling and a crystal melts endothermally on heating. Here we report an opposite occurrence-a liquid\’s endothermic freezing on heating and the resulting crystal\’s exothermic melting on cooling at ambient pressures. C-p decreases on freezing and increases on melting, and the equilibrium temperature meets the thermodynamic requirement. Melting on cooling takes longer than freezing on heating. A rapidly cooled crystal state becomes kinetically frozen, evocative of a nonergodic state. Both C-p and enthalpy relax like those of glasses, though the viscosity is only a few centipoise. The crystal state belongs to energy minima higher than those of the melt, which has consequences for the use of potential-energy landscape, or inherent structures, for a thermodynamic description of a material.


Volume: 123 (5)      Pages from: 051104-1  to: 051104-4

DOI: 10.1063/1.2000228

Citations: 26
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