Interaction-Induced Dipole Moments of Carbon Dioxide

The atmospheric absorption spectrum of carbon dioxide-rich planetary atmospheres, such as Venus or ancient Mars, can be difficult to model due to the presence of collision-induced absorption (CIA) features. These features appear in the 0-250 cm-1 range and are caused by the interaction-induced (I-I) dipole moments of a carbon dioxide dimer. Studying these I-I dipole moments can lead to more accurate atmospheric models, which can be used to create better estimates of the surface temperature of these planets and can reveal information about their paleoclimates. The GAMESS ab initio software package and the NWChem ab initio software package were used with a finite-field approach to calculate the polarizabilities, hyperpolarizabilities, quadrupole moment, and hexadecapole moment for a carbon dioxide monomer. The basis set and bond length dependence of these values were investigated at the Hartree-Fock, MP2, CCSD, and CCSD(T) levels of theory. The energies and dipole moments of a T-shaped CO2 dimer as a function of the intermolecular distance were also calculated. These calculations were performed using the aug-cc-pVTZ, aug-cc-pVQZ, and aug-pc-3 basis sets. Using the monomer results as fitting parameters, a function modeling the counterpoise-corrected dipole moments was developed and compared to an equation developed analytically by M. S. A. El-Kader and G. Maroulis.