Comparative study of electronic-structure methods for platinum-containing molecules: bond lengths and bond dissociation energies

We compare various electronic structure methods including a broad range of density functionals with experimental data on bond lengths and bond dissociation energies available for di- and triatomic platinum-containing molecules. In total we employ 54 GGA, 17 meta-GGA, 36 hybrid, 103 mixed GGA/meta GGA, 17 hybrid, 7 meta hybrid, 10 range-separated hybrid and 5 double hybrid density functionals. Furthermore, the performance of ab initio methods including Hartree-Fock, Moller-Plesset perturbation theory up to fourth order as well as coupled cluster theory up to perturbatively approximated triple excitations, i.e. CCSD(T), is also investigated. In the case of bond lengths, the smallest mean average deviation from experimental values yielding 0.3 pm is found for the hybrid density functional TPSSh. Interestingly, neither recent double hybrid functionals nor ab initio methods result in similar, commensurable accuracies. For the investigated bond dissociation energies, the GGA functional TPSSVWN5 is the closest to experiment with deviations of 6.97 kcal/mol. Finally, we address various possible sources of errors that may explain the large mean average deviation from experiment in the case of CCSD(T) (8.87 kcal/mol), including the effect of basis set size, the influence of the multireference character of the molecular wave function, the quality of the HF determinant as reference wave function and the influence of core electron correlation.