Global transformation of fluid structure and corresponding phase behavior

Abstract

The laws governing the fluid structure transformation from a homogeneous state to the special state in the critical region remain intriguing. In addition, there is a drastic change in the supercritical fluid from a liquid-like type to gas-like when crossing the Widom line, which is still highly debatable. Such challenges require new insights to understand the fluid nature in its entirety. The authors have developed a Two-Phase Hierarchical Model (TPHM), which represents the fluid by a system of various size blocks nested in each other. The TPHM shows that supercritical fluids within a certain region of thermodynamic parameters exist in a form of liquid-like and gas-like clusters (supercritical mesophase) and demonstrates the formation of a hierarchical structure, most pronounced near the critical point. Based on the TPHM, a method for correcting the phase behavior in the critical region is presented, applicable both to pure substances and to multi-component mixtures.