Study on Molecular Dynamics of Singular Nature of Physical Properties near Critical Point in Carbon Dioxide System

Based on the molecular dynamics simulations, this paper analyzed the singular nature of physical properties of the carbon dioxide near the critical point. Detailed analysis of density simulation exhibited that an excellent agreement can be obtained by COMPASS forcefield besides the pseudo-critical region, while the peculiar behavior of density can again be observed. The computational domain is divided into the small sub-domains in which the standard deviation are evaluated as density fluctuation, and it shows maximum near the critical point and higher values at supercritical condition than that at subcritical condition. A new 3-parameter model was put forward to define the CO2 dimer distribution after each molecule in the domain had been supplied with the local coordination frame. The result shows that the T-shaped dimer is with higher probability to be formed than the parallel and crossed configuration, and the conversion of these dimer conformations closely associates with the peculiar properties of the critical point.