Polyamorphism mirrors polymorphism in the liquid–liquid transition of a molecular liquid

Liquid-liquid transitions between two amorphous phases in a single-component liquid (polyamorphism) have defied explanation and courted controversy. All known examples of liquid–liquid transitions have been observed in the supercooled liquid suggesting an intimate connection with vitrification and locally favored structures inhibiting crystallization. However, there is precious little information about the local molecular packing in supercooled liquids meaning that the order parameter of the transition is still unknown. Here, we investigate the liquid–liquid transition in triphenyl phosphite and show that it is caused by the competition between liquid structures that mirror two crystal polymorphs. The liquid–liquid transition is found to be between a geometrically frustrated liquid to a dynamically frustrated glass. These results indicate a general link between polymorphism and polyamorphism and will lead to a much greater understanding of the physical basis of liquid–liquid transitions and allow the discovery of other examples.

单组分液体中两种非晶相之间的液-液转变（多态性，polyamorphism）一直难以解释且颇具争议。所有已知的液-液转变案例均在过冷液体中被观察到，这表明其与玻璃化及抑制结晶的局域优势结构存在密切关联。然而，关于过冷液体中局部分子堆积的信息极为匮乏，这意味着该转变的序参量（order parameter）仍不明确。本文研究了亚磷酸三苯酯中的液-液转变，结果表明该转变由两种镜像晶体多晶型的液体结构之间的竞争所致。研究发现，该液-液转变发生于几何受挫（geometrically frustrated）液体与动力学受挫（dynamically frustrated）玻璃之间。这些结果揭示了多晶型与多态性之间的普遍联系，将极大地增进对液-液转变物理基础的理解，并为发现其他案例提供可能。