Predicting proton transfer barriers with density functional methods

We study the ability of recently developed exchange-correlation functionals to model proton transfer in the H5O2+ model for water and in malonaldehyde . We are particularly interested in assessing the accuracy of the VSXC func tional developed in our research group and compare it to other hybrid funct ionals and high-level wavefunction methods like coupled-cluster theory. We find that VSXC and the hybrid functionals all underestimate proton transfer barriers for H5O2+ but still give a good sense of the overall nature of th e potential energy surface. In malonaldehyde, only VSXC produces a proton t ransfer activation barrier similar to those provided by high-level coupled- cluster methods. (C) 1999 Elsevier Science B.V. All rights reserved.