Supercooled & Glassy Water

The roles of two low temperature and non−crystalline forms of water, (supercooled and glassy water) are very pivotal in supporting the existence of several microorganisms below 0°C, although they are very metastable with respect to the stable crystalline form of water, ice. In the supercooled regime, the hydrogen bond lifetime of a single hydrogen bond and water clusters are found to be significantly higher than in higher temperatures. Diffusion coefficient and configurational entropy show a distinct maximum at density 1.15g/cm3. Two inter−convertible forms of supercooled water, known as Low Density Liquid (LDL) and High Density Liquid (HDL), are found to coexist at temperatures below the freezing point of water. If water is cooled at very fast rate, it becomes glassy, the most profound form of water in the universe, bypassing the formation of ice. Polyamorphism is one of the characteristics observed in glassy water. Glass transition temperature in water has sparked debate in the scientific community. Different experimental procedures as well as water models produced varying values for the glass transition temperatures in water. It has been experimentally monitored and computationally simulated the transition between the two glassy phases of water, HDA and LDA. The transition is terminated at a critical point, according to Liquid−Liquid Critical Point (LLCP) theory. The concept of strong and fragile glasses is very powerful tool in furthering our understanding of the dynamics of glassy materials. It is interesting to note that a transition from strong to fragile occurs in water.