The ozone-water complex: CCSD(T)/CBS structures and anharmonic vibrational spectroscopy of O(HO), (n = 1 - 2).

Ozone-water complexes O(HO) (n = 1-2) have been studied using coupled cluster theory with triple excitations CCSD(T) with correlation consistent basis sets aug-cc-pVnZ (n = D, T, Q) and complete basis set (CBS) extrapolation techniques. We identified seven dimer (n = 1) and nine trimer species (n = 2) with open C and cyclic D ozone. Calculations at the CCSD(T)/CBS level of theory for C O(HO) on the counterpoise (CP)-corrected potential energy surface yield a dissociation energy of D = 2.31 kcal/mol and an O central-oxygen (O) HO oxygen (O) distance r[O⋯O] of 3.097 Å, which is in good agreement with an experimental value of 2.957 Å [J. Z. Gillies et al., J. Mol. Spectrosc. 146, 493 (1991)]. Combining our CCSD(T)/CBS value of D for C O(HO) with our best estimate anharmonic CCSD(T)/aVTZ ΔZPE yields a D value of 1.82 kcal/mol; the CCSD(T)/CBS value of D for D O(HO) is 1.51 kcal/mol and yields an anharmonic CCSD(T)/aVTZ D = 0.99 kcal/mol. CCSD(T)/aVTZ dissociation energies and structures for C O(HO) are D = 4.15 kcal/mol, (D = 3.08 kcal/mol) and r[O⋯O] = 2.973 Å, and D = 2.64 kcal/mol (D = 1.68 kcal/mol) with r[O⋯O] = 2.828 Å for D O(HO). The results from ab initio molecular dynamics simulations, which consider dynamic and thermal effects in O(HO), show that the O(HO) complex remains stable at 50 K and dynamically interconverts between two hydrogen-bonded conformers with short O⋯O contacts (3.85 Å). Carr-Parrinello molecular dynamic (CPMD) simulations for O(HO) and O(HO) at 100 K demonstrate that O(HO) remains structurally intact, whereas O(HO) dissociates to free ozone and water, a feature consistent with the larger average binding energy in O(HO) (2.2 kcal/mol) vs that in O(HO) (1.8 kcal/mol). Finally, the results from CCSD(T)/CBS and CPMD simulations demonstrate that the large inter-trimer binding energies in O(HO) would give rise to an elevated trimer/dimer population ratio, making O(HO) a particularly stable and spectroscopically detectable complex.