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Enhanced Crystal Nucleation in Glass-Forming Liquids by Tensile Fracture in the Glassy State

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journal contribution
posted on 03.12.2018, 00:00 by Yuan Su, Lian Yu, Ting Cai
Crystal nucleation in a supercooled liquid typically attains its maximal rate near the glass transition temperature Tg and slows down with further cooling, becoming exceedingly slow in the glassy state. We report that cooling a liquid well below its Tg can actually increase the rate of nucleation because of tensile fracture. Cooling liquid griseofulvin (an antifungal drug) approximately 80 K below its Tg induces extensive network fracture due to tensile stress from a thermally less expansive container, and reheating the sample above Tg leads to crystallization that otherwise would not occur. An extensive statistical study revealed a direct connection between fracture and crystal nucleation. This phenomenon explains puzzling results in the literature concerning anomalous nucleation in deeply supercooled liquids and is relevant for selecting storage conditions to ensure the physical stability of amorphous drugs.