Dielectric Constant and Density Dependence of the Structure of Supercritical Carbon Dioxide Using a New Modified Empirical Potential Model:  A Monte Carlo Simulation Study

Abstract

Two modified versions of the Elementary Physical Model (EPM) [J. Phys. Chem. 1995, 99, 12021] for supercritical carbon dioxide have been proposed in this work and their validities are affirmed by computing the thermodynamic properties and dielectric constant up to 910 kg/m3 with use of canonical ensemble Monte Carlo simulation. Simulations performed for 500 molecules with the EPM2-M model reproduce the experimental data accurately at all thermodynamic states. The structural analyses demonstrate that the aggregation is strong at low density while the coordination number is large at high density. In addition, a detailed study on the radial and angular correlation functions reveals that the T-shaped geometry is dominate while a variety of other structures still appear in the first coordination shell. Furthermore, the angular correlation functions show that the probability of a molecule being oriented toward the convex side of another molecule is equal to that pointing toward the concave side since the molecular nonlinearity of carbon dioxide is only marginal. As the distance between two molecules increases, the preferred orientations disappear quickly and all the results are in good agreement with the prior ab initio calculation [J. Chem. Phys. 2004, 120, 9694].

Molecular Dynamics Simulation of Transport and Structural Properties of CO2 Using Different Molecular Models

“…Here, the cutoff distance is defined as 4 Å. 44 That is to say, CO 2 dimer is formed if the distance between two carbon atoms is less than 4 Å. The percentages of multimers as a function of the cluster size are calculated to know the microscopic distributions of CO 2 molecules at various temperatures and pressures, and the results are plotted in Figure 11.…”

A first principles approach to the electronic properties of liquid and supercritical CO2

“…In comparison with scCO 2 , N[cosθ] for liquid CO 2 shows a slightly faster decay to zero what reflects some smaller deviations from linearity of the CO 2 monomers. This value of θ is also the same used by Zhang et al 29 in a modified version of the EPM model 26 for CO 2 . Therefore, our results suggest, in keeping with other results from the literature, some deviations from the linear configuration for CO 2 in condensed phases.…”

Oil extraction from microalgae for biodiesel production

“…The dielectric constant or the solvent polarity of a supercritical fluid measures the degree of interaction between the solvent and the organic molecules (Zhang et al, 2005). Table 2 shows the exponential dependence of lipid mass transfer coefficient (k) during our SCCO 2 extractions on fluid dielectric constant along an isotherm.…”