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Quantifying the performance of conventional DFT methods on a class of difficult problems: The interaction (hyper)polarizability of two water molecules as a test case

We have investigated the predictive capability of a widely used group of density functional theory (DFT) methods on the interaction (hyper)polarizability of the two water molecules in the water dimer. We find that compared with conventional ab initio methods, DFT gives a different picture of the dipole moment and (hyper) polarizability for the water monomer and dimer. In addition, the DFT methods tested in this work predict for the water dimer a systematically higher value of the differential interaction-induced second hyperpolarizability per water molecule, DHPM ¼ ( c(H2O)2)/2 � c (H2O) than the ab initio ones. The interaction-induced mean polarizability and second hyperpolarizability is predicted to be small and positive for all DFT methods used here. The respective quantities predicted by conventional post-Hartree-Fock ab initio methods are also quite small but negative. V C 2011 Wiley Periodicals, Inc. Int J Quantum Chem 000: 000-000, 2011