Ab initio potential energy surface for the carbon dioxide molecule pair and thermophysical properties of dilute carbon dioxide gas

A four-dimensional intermolecular potential energy surface (PES) for two rigid carbon dioxide molecules was determined from quantum-chemical ab initio calculations. Interaction energies for 1229 CO2–CO2 configurations were computed at the CCSD(T) level of theory using basis sets up to aug-cc-pVQZ supplemented with bond functions. An analytical site-site potential function with seven sites per CO2 molecule was fitted to the interaction energies. The PES was validated by calculating the second virial coefficient as well as viscosity and thermal conductivity in the dilute-gas limit.