Systematic CASPT2 analysis of the geometry and force field of ozone with extrapolation to the infinite basis set

An efficient procedure, based on the CASPT2 method using Dunning’s correlation-consistent bases and extrapolation to the limit of infinite basis, is proposed for studying difficult multiconfigurational species. The procedure is evaluated by calculating the ground state geometry, harmonic wavenumbers and quadratic and cubic force constants of ozone. The best results are obtained with the full-outer-valence (12,9) active space and extrapolation from Dunning’s weighted core-valence basis sets. The quality of these results, obtained using only modest computational resources, is comparable to computationally far more demanding treatments.