(686b) Gaussian Charge Polarizable Model of Carbon Dioxide

Carbon dioxide molecules are characterized by high anisotropic polarizability (a_ax = 27.25 au, a_eq = 13.018 au [1]). A proper description of polarization effects is known to be essential in heterogenous systems involving phase equilibria and interactions with polar species, such as in environments expected at CO₂ sequestration sites. While for water with lower polarizability (9.785 au), multiple polarizable models have been developed, none currently exists for carbon dioxide.

In this presentation we describe the development of a new CO₂ model, Gaussian Charge Polarizable Model (GCPM), and its validation in various environments. For compatibility purposes, our methodology follows closely the development of the GCPM of water [2]. Atomic charges and polarizabilities are set so that the monomer quadrupole moment and anisotropic polarizability reproduce exactly experimental data. To model the anisotropy we allow the three polarizable sites located on the three atoms of the molecule to interact with each other. To prevent a polarization catastrophe the interaction is modulated using Gaussian charges [3]. Non-Coulombic interactions are then optimized based on dimer properties obtained from ab initio calculations, and structure and thermodynamics obtained from experiments. The applicability of the model is extended by parametrization of cross GCPM CO₂ / GCPM water interactions and predictions are verified through the comparison of water-CO₂ mixture simulations with experiment.

This research was supported by the US Department of Energy, Office of Basic Energy Sciences as part of the Energy Frontier Research Center for Nanoscale Control of Geologic CO₂.

[1] Bridge, N.J.; Buckingham, A.D.; Proc. R. Soc., Ser. A 295 (1966) 334. [2] Paricaud, P.; Predota, M.; Chialvo, A.A.; Cummings, P.T.; J. Chem. Phys. 122 (2005) 24451. [3] Elking, D.; Darden, T.; Woods, J. R.; J. Comput. Chem. 28(7), (2007) 1261.