Spontaneous liquifaction of isomerizable molecular crystals

Year: 2007

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

Autors Affiliation: Istituto per i Processi Chimico-Fisici del CNR, 56124 Pisa, Italy; Department of Materials Science and Engineering, McMaster University, Hamilton, Ont. L8S 4L7, Canada

Abstract: A lattice vacancy raises the energy of the neighboring (flexible) molecule in a crystal, which may be enough to isomerize it to a tautomer that does not fit the lattice site, thus creating a liquidlike local region embedding the vacancy. Similar regions may appear elsewhere in the lattice and the regions may ultimately merge. Thus a crystal may spontaneously liquefy over a period of hours to years at a temperature below its normal melting point. Simultaneous heat capacity and heat absorption measurements of several such molecular crystals show that they spontaneously liquefy at a temperature far below their reputed melting point, according to a non-exponential rate kinetics and a temperature dependent rate constant, and do not crystallize on cooling.


Volume: 126 (2)      Pages from: 021107-1  to: 021107-4

DOI: 10.1063/1.2432345

Citations: 17
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