A “first principles” many-body carbon dioxide potential energy function (mbCO2) is developed for CO2 gas and condensed phase systems. The mbCO2 potential was originally constructed as a dimer potential function with flexible-monomers calculated at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Recently, we have included three-body contributions, expressed as the sum of permutationally invariant polynomials and the Axilrod-Teller-Muto three-body function, and derived from a fit to over 15,000 CO2 trimer configurations calculated at the CCSD(T)-F12a/aug-cc-pVDZ level. With the updated many-body potential, we revisit the optimization of CO2 clusters as well as the energetic ordering of trimers. Anharmonic frequencies are determined using correlated vibrational structure methods and compared to experimental values with special attention directed at the intermolecular modes of vibration. Lastly, we extend our application of the mbCO2 potential to the structure and thermodynamic properties of crystalline CO2 in its low-pressure cubic phase.

Development of a many-body carbon dioxide potential to explore the electronic and vibrational structure of gas and condensed phase CO2

255th National Meeting (2018)

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