The Rehiss Three-Range Exchange Functional With An Optimal Variation Of Hartree-Fock And Its Use In The Rehissb-D Density Functional Theory Method

In the present study, we have reparametrized the HISS exchange functional. The new "reHISS" exchange provides a balance between short- and mid-range Hartree-Fock exchange (HFX) and a large total HFX coverage, with a fast convergence to zero HFX in the long range. The five parameters in this functional (according to equations 3 and 4 in the main text) are c(SR) = 0.15, c(MR) = 2.5279, c(LR) = 0, omega(SR) = 0.27, and omega(LR) = 0.2192. The combination of reHISS exchange with a reparametrized B97c-type correlation functional (Chan et al., J. Comput. Chem. 2017, 38, 2307) and a D2 dispersion term (s(6) = 0.6) gives the reHISSB-D method. We find it to be more accurate than related screened-exchange methods and, importantly, its accuracy is more uniform across different properties. Fundamentally, our analysis suggests that the good performance of the reHISS exchange is related to it capturing a near-optimal proportion of HFX in the range of interelectronic distance that is important for many chemical properties, and we propose this range to be approximately 1-4 angstrom. (C) 2018 Wiley Periodicals, Inc.