Polyamorphism in Liquids and Amorphous Substances: An Analogue of Polymorphism in Crystalline Solids

Abstract

Transition of a crystalline substance from one kind of structural arrangement of atoms to another as a function of external actions like pressure and/or temperature without any change in composition, described as polymorphism, is a very well-known phenomenon. Similar transitions in case of amorphous solids or the corresponding melts (currently called “polyamorphism”), as also possibilities of such transitions have been indicated in various reports in historically early, intermediate and new literature. Recent endeavours have led to systematic studies on a series of liquids and solids, yielding clear proof of first order transition in several cases (e.g. liquid water and silicon, as also specific glassy aluminates), and indications of such isochemical transformations in various other liquid or solid substances. The plan of the present article is to offer a current scenario of the happenings in this area, list up some of the common features of the candidate species (as a guideline for identification of possible new candidates) and discuss possible applications of polyamorphism in materials science and technology.

Keywords:

• Polyamorphism
• Liquid-liquid transitions
• Solid-solid transitions
• Strong and fragile liquids
• Water
• Silicon
• Silica
• Yttrium aluminates