Long-Range-Corrected Hybrids Based on a New Model Exchange Hole

By admixing a fraction of exact Hartree-Fock-type exchange with conventional semilocal functionals, global hybrids greatly improve the accuracy of Kohn-Sham density functional theory. However, because global hybrids exhibit incorrect asymptotic decay of the exchange-correlation potential, they can have large errors for diverse quantities such as reaction barrier heights, nonlinear optical properties, and Rydberg and charge-transfer excitation energies. These errors can be removed by using a long-range-corrected hybrid, which uses exact exchange in the long range. Evaluating the long-range-corrected exchange energy requires a model for the semilocal exchange hole, and such models are scarce. Recently, two of us introduced one such model (J. Chem. Phys. 2008, 128, 194105). This model obeys several exact constraints and was designed specifically for use in long-range-corrected hybrids. Here, we give sample results for three long-range-corrected hybrids based upon our exchange hole model and show how the model can easily be applied to any generalized gradient approximation (GGA) for the exchange energy to create a long-range-corrected GGA.