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Summary: On the accuracy of density-functional theory exchange-correlation
functionals for H bonds in small water clusters:
Benchmarks approaching the complete basis set limit
Biswajit Santra
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Angelos Michaelidesa
Materials Simulation Laboratory, London Centre for Nanotechnology and Department of Chemistry,
University College London, London WC1E 6BT, United Kingdom
and Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Matthias Scheffler
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Received 13 July 2007; accepted 4 September 2007; published online 9 November 2007
The ability of several density-functional theory DFT exchange-correlation functionals to describe
hydrogen bonds in small water clusters dimer to pentamer in their global minimum energy
structures is evaluated with reference to second order Møller-Plesset perturbation theory MP2 .
Errors from basis set incompleteness have been minimized in both the MP2 reference data and the
DFT calculations, thus enabling a consistent systematic evaluation of the true performance of the
tested functionals. Among all the functionals considered, the hybrid X3LYP and PBE0 functionals
offer the best performance and among the nonhybrid generalized gradient approximation
functionals, mPWLYP and PBE1W perform best. The popular BLYP and B3LYP functionals
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