Gaussian charge polarizable interaction potential for carbon dioxide

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Thermodynamics

Background:

• Accurate molecular interaction potentials are crucial for predicting thermophysical properties of fluids like carbon dioxide (CO2).
• Existing simple pair potentials often fail to adequately describe the behavior of CO2, particularly its virial coefficients.

Purpose of the Study:

• To investigate the performance of various simple pair interaction potentials for carbon dioxide.
• To develop and validate a more accurate molecular model for carbon dioxide, capable of reproducing experimental thermodynamic data.

Main Methods:

• Evaluation of several simple pair interaction potentials for their ability to predict second and third virial coefficients of CO2.
• Development of a rigid, polarizable, three-site interaction potential incorporating modified Buckingham exp-6, anisotropic Axilrod-Teller correction, and Gaussian charge densities.
• Validation of the developed potential against experimental data for CO2 density and comparison with quantum-mechanical calculations for dimer and hydrated complexes.

Main Results:

• Simple pair potentials were found to underestimate the second virial coefficient by up to 20% and the third virial coefficient.
• The developed three-site polarizable potential accurately reproduces experimental second and third virial coefficients within a few percent.
• The model also shows good agreement with experimental CO2 fluid densities and qualitative agreement with trimer stability when quantum corrections are included.

Conclusions:

• A rigid, polarizable, three-site interaction potential offers a significant improvement over simple pair potentials for modeling carbon dioxide.
• This advanced model accurately predicts key thermodynamic properties and provides better structural insights into CO2 interactions, including hydrated complexes.