Many crystalline materials form polymorphs and undergo solid–solid transitions between different forms as a function of temperature or pressure. However, there is still a poor understanding of the mechanism of transformation. Conclusions about the transformation process are typically drawn by comparing the crystal structures before and after the conversion, but gaining detailed mechanistic knowledge is strongly impeded by the generally fast rate of these transitions. When the crystal morphology does not change, it is assumed that crystallinity is maintained throughout the process. Here we report transformation between polymorphs of ZnCl₂(1,3-diethylimidazole-2-thione)₂ which are sufficiently slow to allow unambiguous assignment of single crystal to single crystal transformation with shape preservation proceeding through an amorphous intermediate phase. This result fundamentally challenges the commonly accepted views of polymorphic phase transition mechanisms.

中文翻译：

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形状保持单晶到无定形到单晶多晶型转变是可能的

许多结晶材料形成多晶型物并随着温度或压力在不同形式之间经历固-固转变。然而，人们对转化的机制仍然知之甚少。关于转变过程的结论通常是通过比较转变前后的晶体结构得出的，但是这些转变的普遍快速速度极大地阻碍了获得详细的机械知识。当晶体形态不改变时，假定在整个过程中保持结晶度。在这里，我们报告了 ZnCl ₂ (1,3-diethylimidazole-2-thione) _{2多晶型物之间的转化}它们的速度足够慢，可以明确地将单晶分配给单晶转变，并通过无定形中间相进行形状保持。这一结果从根本上挑战了普遍接受的多态相变机制观点。