Predicting the binding energies of H-bonded complexes: A comparative DFT study

Abstract

Comparisons with the results of coupled cluster calculations were made to assess the quality of density functionals in predicting the electronic binding energies of H-bonded complexes. A variety of different density functionals, namely B3LYP, B97-1, PBE0, HCTH, BLYP, PBE, LDA and a recently derived improvement of the HCTH functional (HCTH38), as well as the standard abinitio Hartree–Fock and second-order Møller–Plesset perturbation theory methods were applied using a triple-ζ plus double polarisation basis set. Equilibrium structures, counterpoise corrected binding energies and harmonic frequencies were calculated for the (HF)₂, (HCl)₂, (H₂O)₂, (CO)(HF), (OC)(HF), (FH)(NH₃), (ClH)(NH₃), (H₂O)(NH₃) and (H₃O⁺)(H₂O) complexes. Although the hybrid methods performed well in general, the new HCTH38 functional as a pure GGA predicted binding energies of better quality than the B3LYP functional. Bond length changes and frequency shifts were compared to MP2 results.