Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water

TL;DR

This study investigates how pressure influences the fragile-to-strong dynamic transition in supercooled confined water, providing evidence for a possible second critical point where the transition ceases.

Contribution

It demonstrates the pressure dependence of the fragile-to-strong transition in supercooled water and suggests the existence of a second critical point at high pressure.

Findings

F-S transition temperature decreases with pressure

Transition intersects the nucleation line at 1600 bar

Possible second critical point identified

Abstract

By confining water in nano-pores of silica glass, we can bypass the crystallization and study the pressure effect on the dynamical behavior in deeply supercooled state using neutron scattering. We observe a clear evidence of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that the transition temperature decreases steadily with an increasing pressure, until it intersects the homogenous nucleation temperature line of bulk water at a pressure of 1600 bar. Above this pressure, it is no longer possible to discern the characteristic feature of the F-S transition. Identification of this end point with the possible second critical point is discussed.