Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 26: Methods: Electronic Structure Theory
O 26.3: Vortrag
Dienstag, 26. Februar 2008, 11:45–12:00, MA 042
On the accuracy of DFT exchange-correlation functionals for H bonds in small water clusters: Benchmarks approaching the complete basis set limit — •Biswajit Santra1, Angelos Michaelides1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. — 2London Centre for Nanotechnology and Department of Chemistry, University College London, London WC1E 6BT, UK.
The ability of DFT exchange-correlation functionals to describe H bonds between H2O molecules remains an important open question. Here, we address this issue through a series of studies of small gas phase water clusters. Using Møller-Plesset perturbation theory (MP2) as our reference, we have assessed the abilities of 16 DFT xc functionals to describe the energetics of the low energy isomeric structures of water dimers, trimers, tetramers, and pentamers. Errors from basis set incompleteness have been minimized in both the MP2 reference data and the DFT calculations, thus, enabling a systematic evaluation of the true performance of the tested functionals. Among the functionals considered, the hybrid X3LYP and PBE0 functionals are the best: predicting H bond strengths within 10 meV (∼0.3 kcal/mol) of MP2. Of the nonhybrid GGA functionals, mPWLYP and PBE1W perform the best. The popular BLYP and B3LYP functionals consistently underbind. PBE, PW91, and TPSS display rather variable performance with cluster size, leading us to conclude that results from dimers and trimers alone are insufficient to determine the general abilities of a given functional.