Evidence of the existence of the high-density and low-density phases in deeply-cooled confined heavy water under high pressures.

Abstract

The average density of D2O confined in a nanoporous silica matrix (MCM-41-S) is studied with neutron scattering. We find that below ~210 K, the pressure-temperature plane of the system can be divided into two regions. The average density of the confined D2O in the higher-pressure region is about 16% larger than that in the lower-pressure region. These two regions could represent the so-called "low-density liquid" and "high-density liquid" phases. The dividing line of these two regions, which could represent the associated 1st order liquid-liquid transition line, is also determined.