Thermodynamics of Supercooled Water

We present the currently available experimental information for the thermodynamic properties of supercooled ordinary and heavy water and the possibility of modeling these thermodynamic properties on a theoretical basis. Part of the interest into the thermodynamic behavior of supercooled water is caused by an anomalous temperature dependence of the heat capacity, the compressibility and the thermal expansivity. We show that by assuming the existence of a virtual liquid--liquid critical point in supercooled water, the theory of critical phenomena can give an accurate account of the experimental thermodynamic-property data up to a pressure of 150~MPa. In addition, we show that a semi-empirical extension of the theoretical model can account for all currently available experimental data in the supercooled region, up to 400~MPa. Critical-point thermodynamics describes the available thermodynamic data on supercooled water within experimental accuracy, thus establishing a benchmark for any further developments in this area.