Development of a Flexible-Monomer Two-Body Carbon Dioxide Potential and Its Application to Clusters up to (CO₂ )₁₃

A flexible-monomer two-body potential energy function was developed that approaches the high level CCSD(T)/CBS potential energy surface (PES) of carbon dioxide (CO₂ ) systems. This function was generated by fitting the electronic energies of unique CO₂ monomers and dimers to permutationally invariant polynomials. More than 200,000 CO₂ configurations were used to train the potential function. Comparisons of the PESs of six orientations of flexible CO₂ dimers were evaluated to demonstrate the accuracy of the potential. Furthermore, the potential function was used to determine the minimum energy structures of CO₂ clusters containing as many as 13 molecules. For isomers of (CO₂ )₃ , the potential demonstrated energetic agreement with the M06-2X functional and structural agreement of the B2PLYP-D functional at substantially reduced computational costs. A separate function, fit to MP2/aug-cc-pVDZ reference energies, was developed to directly compare the two-body potential to the ab initio MP2 level of theory. © 2017 Wiley Periodicals, Inc.