Determination of Molecular Diameter by PVT

Abstract

We derive an equation for calculation of molecular diameter of dense fluids, with using simultaneous Lennard-Jones (12-6) potential function and the internal pressure results. Considering the internal pressure by modeling the average configurational potential energy and then taking its derivative with respect to volume to a minimum point of potential energy has been shown that molecular diameter is function of the resultant of the forces of attraction and the forces of repulsion between the molecules in a fluid. The regularity is tested with experimental data for 10 fluids including Ar, N2, CO, CO2, CH4, C2H6, C3H8, C4H10, C6H6, and C6H5CH3. These problems have led us to try to establish a function for the accurate calculation of the molecular diameter based on the internal pressure theory for different fluids. The relationship appears to hold both compressed liquids and dense supercritical fluids.