The anharmonic vibrational structure of small van der Waals complexes including the carbon dioxide dimer and trimer and the carbon dioxide and argon dimer are explored using a flexible-monomer many-body potential energy function (PEF). The originally developed potential was intended to treat only carbon dioxide at the two-body level. Yet, recent improvements to the PEF currently allow for higher order expansion terms and heterogeneous systems. This new function has been integrated into existing vibrational structure programs, where specifically vibrational correlation approaches such as VSCF, VMP2, and VCI are employed. Results at the vibrational configuration interaction level agree to within a few wavenumbers of the experimentally determined peaks in both the intramolecular and intermolecular regions of the experimental spectra. Our results also suggest Fermi resonance in the low-frequency region of the CO2 dimer due to mixing between overtone (2νa) and fundamental (νc) bands. Lastly, we note how different low-lying configurations of the van der Waals complexes may be identified via our computed vibrational spectra.

Investigating the anharmonic vibrational structure of van der Waals systems

2019 Spring National Meeting

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