The Linear Chain Clusters in Real Gases

The chapter describes the new class of linear chain clusters, discovered by the author, and the methods of their properties evaluation. In real gases exist different types of clusters: linear with a minimal number of bonds between particles and tightly bound two and three dimensional clusters. The experimental data analysis for many pure gases shows wide zones of temperature and density, where the linear chain clusters dominate. The potential energy density series expansion by the monomer fraction density at moderate densities of real gases returns cluster bond parameters and their equilibrium constants, which may be attributed to this new class of clusters. The monomer fraction density based computer aided analysis of precise thermophysical data for pure fluids discovers wonderful properties of these unknown cluster structures in real gases. An extrapolation of these loosely bound clusters' properties to larger densities provides a selection of densely bound three dimensional clusters in sub- and supercritical fluids in general and especially in the CO2. It is important to know the clusters structure and parameters in this gas, widely used in supercritical fluid technologies. Step-by-step movement from diluted to dense gases discovers properties of large three dimensional clusters with numbers n of particles up to the level of one thousand. The logarithmic method to estimate the averaged numbers n of particles in three dimensional clusters is developed to study the mechanism of the soft structural transition between dominating cluster fractions with neighbor numbers n and between the gas-like and liquid-like supercritical fluids.