Gaussian-Charge Polarizable Interaction Potential for Carbon Dioxide

TL;DR

This paper introduces a polarizable interaction potential for carbon dioxide that accurately reproduces experimental virial coefficients and fluid densities, improving upon simpler models by including anisotropic and inducible dipole effects.

Contribution

The paper presents a novel, rigid, polarizable three-site potential for CO2 that incorporates Gaussian charge densities and anisotropic corrections, achieving high accuracy in thermodynamic property predictions.

Findings

Reproduces second and third virial coefficients within a few percent.

Accurately predicts fluid density at various pressures and temperatures.

Shows passable agreement with quantum-mechanical calculations for molecular structures.

Abstract

A number of simple pair interaction potentials of the carbon dioxide molecule are investigated and found to underestimate the magnitude of the second virial coefficient in the temperature interval 220 K to 448 K by up to 20%. Also the third virial coefficient is underestimated by these models. A rigid, polarizable, three-site interaction potential reproduces the experimental second and third virial coefficients to within a few percent. It is based on the modified Buckingham exp-6 potential, an anisotropic Axilrod-Teller correction and Gaussian charge densities on the atomic sites with an inducible dipole at the center of mass. The electric quadrupole moment, polarizability and bond distances are set to equal experiment. Density of the fluid at 200 and 800 bars pressure is reproduced to within some percent of observation over the temperature range 250 K to 310 K. The dimer structure is in passable agreement with electronically resolved quantum-mechanical calculations in the literature, as are those of the monohydrated monomer and dimer complexes using the polarizable GCPM water potential. Qualitative agreement with experiment is also obtained, when quantum corrections are included, for the relative stability of the trimer conformations, which is not the case for the pair potentials.