Molecular dynamics simulation on the local density distribution and solvation structure of supercritical CO2 around naphthalene

Abstract

Molecular Dynamics (MD) simulations were performed to understand the solvation structure and the mechanistic nature of the divergence of partial molar volume ((nu) over tilde (infinity)(2)) near the critical point. Isothermal-isobaric (NpT) simulations were carried out at T-r = 1.03 from p(r) = 0.87 to p(r) = 3.72 with the truncated and shifted Leonard-Jones and the Weeks-Chandler-Andersen (WCA) potentials. A statistical analysis on the structural characters was carried out to investigate the origin of the divergent (nu) over tilde (infinity)(2) near the critical point. The result suggested that no distinct cluster structure exists. Rather, a solute enters the pre-existent high-density and/or low-density domain and its preference depends on the magnitude of the solute/solvent attractive interaction. The influence of the attractive forces is propagated via the density fluctuation throughout the entire system. Thus, the interplay between the solute/solvent attraction and the pre-existent density fluctuation is the mechanistic origin of the divergence of (nu) over bar (infinity)(2) near the critical point.