Evaluation of B3LYP, X3LYP, and M06-class density functionals for predicting the binding energies of neutral, protonated, and deprotonated water clusters
Abstract
In this paper we assess the accuracy of the B3LYP, X3LYP, and newly developed M06-L, M06-2X, and M06 functionals to predict the binding energies of neutral and charged water clusters including (H_2O)_n, n = 2−8, 20), H_3O+(H_2O_)n, n = 1−6, and OH−(H_2O)_n, n = 1−6. We also compare the predicted energies of two ion hydration and neutralization reactions on the basis of the calculated binding energies. In all cases, we use as benchmarks calculated binding energies of water clusters extrapolated to the complete basis set limit of the second-order Møller−Plesset perturbation theory with the effects of higher order correlation estimated at the coupled-cluster theory with single, double, and perturbative triple excitations in the aug-cc-pVDZ basis set. We rank the accuracy of the functionals on the basis of the mean unsigned error (MUE) between calculated benchmark and density functional theory energies. The corresponding MUE (kcal/mol) for each functional is listed in parentheses. We find that M06-L (0.73) and M06 (0.84) give the most accurate binding energies using very extended basis sets such as aug-cc-pV5Z. For more affordable basis sets, the best methods for predicting the binding energies of water clusters are M06-L/aug-cc-pVTZ (1.24), B3LYP/6-311++G(2d,2p) (1.29), and M06/aug-cc-PVTZ (1.33). M06-L/aug-cc-pVTZ also gives more accurate energies for the neutralization reactions (1.38), whereas B3LYP/6-311++G(2d,2p) gives more accurate energies for the ion hydration reactions (1.69).
Additional Information
© 2009 American Chemical Society. Received December 10, 2008; publication date (web): 12 March 2009. We are grateful to Dr. George S. Fanourgakis, Dr. Daniel Svozil, and Dr. P. Tarakeshwar for providing us with the Cartesian coordinates of (H_(2)O)_(20), H_(3)O+(H_(2)O)_(6)OH^−, and OH^−(H_(2)O)_(5−6) clusters, respectively. This work was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy's Office of Biological and Environmental Research located at the Pacific Northwest National Laboratory, which is operated for the Department of Energy by Battelle. Supporting Information Cartesian coordinates and energies for optimized clusters at the B3LYP/6-311++G(2d,2p) level of theory and Table 1S comparing the performance of the various DFT methods employing the 6-311++G** basis set. This material is available free of charge via the Internet at http://pubs.acs.org.Attached Files
Supplemental Material - ct800549f_si_001.pdf
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Additional details
- Eprint ID
- 14277
- Resolver ID
- CaltechAUTHORS:20090520-112111336
- Department of Energy (DOE)
- Created
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2009-08-13Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field