Search for the superiority of supercritical water with ab initio molecular dynamics simulation

Water, from ambient state to supercritical state, plays diverse roles in various reactions. Especially, supercritical water appears more attractive for scientific and engineering applications, due to its unique physicochemical properties. Herein, by using ab initio molecular dynamic method, we studied the various structures and charge characteristics of the supercritical water with different densities mainly and compared it with multi-state water from 300 K to 800 K. The results demonstrate that supercritical water has a looser structure and weaker polarity than liquid water, and the decreasing density of supercritical water will enhance such a tendency, which promote the solubility of organics in it and the reactivity of water. What's more interesting is the mutation of hydrogen bonds and spectrum while the temperature rises to cross the supercritical point. For supercritical water, the molecules are mostly monomers, and the vibrational mode is close to but still lower than that of the gas phase. The calculated parameters of supercritical water are close to the actual applications, which is demonstrated by the complete gasification of the model compounds, diphenylethane, in experiments. Moreover, this work provides a reference for research and development of the wide application of supercritical water in practice.