Structure and stability of the Na+·CO2 and Na+·H2O complexes

The geometries and harmonic vibrational frequencies of the Na+·H2O and Na+·CO2 complexes are calculated at high levels of ab initio theory (B3LYP, QCISD) using the aug-cc-pVTZ basis set. In addition the binding energies are calculated at the CCSD and CCSD(T) levels of theory using the aug-cc-pVQZ and aug-cc-pV5Z basis sets, with the CCSD(T)/aug-cc-pV5Z results being estimated. These two sets of results are then used to derive the thermodynamic quantities for the clustering reactions, ΔH0 and ΔS0. The T-shaped C2v saddle point of Na+·CO2 is briefly investigated.