To uncover the way Hartree-Fock exchange brings static correlation error into hybrid Kohn-Sham density functional theory, we compare the potential energy curves of four diatomic molecules, namely, H2, F2, HF, and NaF, using both restricted and unrestricted Kohn-Sham theory. We find that increasing the percentage of Hartree-Fock exchange significantly increases the static correlation error because Hartree-Fock exchange replaces the ability of local exchange in density functionals to account for the localization effects associated with static correlation.
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We thank Pragya Verma for helpful feedback on the manuscript. This research was supported as part of the Nanoporous Materials Genome Center by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under award DE-FG02-17ER16362 as part of the Computational Chemical Sciences Program.
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