Increasing the applicability of DFT I: Non-variational correlation corrections from Hartree-Fock DFT for predicting transition states

► DFT functional evaluated with HF density provides good measure of electron correlation. ► HF-DFT offers a very easy, inexpensive calculation suited to large molecules. ► Analytical gradients for HF-DFT is formulated and applied. ► Barrier heights comparisons are done for HF, KS-DFT, HF-DFT, CCSD (T), and ?CCSD (T). ► HF-DFT outperforms KS-DFT in barrier height determination.