VERIFICATION OF A MECHANISM FOR NUCLEATING CRYSTALLIZATION OF SUPERCOOLED LIQUIDS

Earlier work has suggested that the melting temperature of crystals which undergo volume expansion on melting, is raised when the crystals are clamped between two layers of material thereby trapping them in regions of high pressure. These trapped crystals may then be used to nucleate the crystallization of the corresponding supercooled liquids. The maximum pressure to which the crystals can be subjected is given by the hardness of the trapping material and the maximum temperature to which these trapped crystals can be exposed without melting should represent the melting point of the crystals at this elevated pressure. In order to test the validity of this hypothesis, the method is used in an attempt to determine the high pressure melting points of benzophenone, diphenylamine and phenyl salicylate. The data have been fitted to the Simon equation and a comparison made to the known high pressure melting points for these compounds. Although the temperatures determined using this method are somewhat lower that the predicted melting points, explanations are advanced to account for this, and the results are shown to be entirely consistent with the original hypothesis. © 1990.