Atmospheres of carbon dioxide-rich planets, such as Mars or Venus, can be difficult to model due to the presence of collision-induced absorptions, which occur in the 0-250 cm-1 range. Collision-induced absorptions of carbon dioxide are caused by interaction-induced (I-I) dipole moments of two carbon dioxide molecules, and understanding these dipole moments can help lead to more accurate atmospheric models. These I-I dipole moments are dependent upon the polarizability and hyperpolarizability of the CO2 monomer and dimer. The GAMESS ab initio software package was used to investigate the basis set dependence of the polarizability and the hyperpolarizability of CO2. The cc-pVNZ, aug-cc-pVNZ, and d-aug-cc-pVNZ families of basis sets were used, along with the pc-3, aug-pc-3, and aug-pc-4 basis sets. Using a finite field approach, we have also calculated the energy of a single CO2 molecule, in a uniform electric field, at various bond lengths. These calculations were performed at the Hartree-Fock, MP2, and CCSD(T) levels of theory, and the results were compared to each other. We then estimated the polarizability and the hyperpolarizability from the energies using an equation described by A. D. Buckingham.

Basis set dependence of carbon dioxide polarizability and hyperpolarizability using ab initio methods

255th National Meeting (2018)

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