Thermodynamics of Fluid Polyamorphism

0491218 - ÚT 2019 RIV US eng J - Journal Article
Anisimov, M. A. - Duška, Michal - Caupin, F. - Amrhein, L. E. - Rosenbaum, A. - Sadus, R. J.
Thermodynamics of Fluid Polyamorphism.
Physical Review X. Roč. 8, č. 1 (2018), č. článku 011004. ISSN 2160-3308. E-ISSN 2160-3308
Institutional support: RVO:61388998
Keywords : liquid phase-transition * supercooled water * high-pressure
OECD category: Physical chemistry
Impact factor: 12.211, year: 2018

Fluid polyamorphism is the existence of different condensed amorphous states in a single-component fluid. It is either found or predicted, usually at extreme conditions, for a broad group of very different substances, including helium, carbon, silicon, phosphorous, sulfur, tellurium, cerium, hydrogen, and tin tetraiodide. This phenomenon is also hypothesized for metastable and deeply supercooled water, presumably located a few degrees below the experimental limit of homogeneous ice formation. We present a generic phenomenological approach to describe polyamorphism in a single-component fluid, which is completely independent of the molecular origin of the phenomenon. We show that fluid polyamorphism may occur either in the presence or in the absence of fluid phase separation depending on the symmetry of the order parameter. In the latter case, it is associated with a second-order transition, such as in liquid helium or liquid sulfur. To specify the phenomenology, we consider a fluid with thermodynamic equilibrium between two distinct interconvertible states or molecular structures. A fundamental signature of this concept is the identification of the equilibrium fraction of molecules involved in each of these alternative states. However, the existence of the alternative structures may result in polyamorphic fluid phase separation only if mixing of these structures is not ideal. The two-state thermodynamics unifies all the debated scenarios of fluid polyamorphism in different areas of condensed-matter physics, with or without phase separation, and even goes beyond the phenomenon of polyamorphism by generically describing the anomalous properties of fluids exhibiting interconversion of alternative molecular states.
Permanent Link: http://hdl.handle.net/11104/0285257