title: Testing Exact Upper Bounds to Exact Exchange.
abstract: The exact exchange energy and its energy density are useful but computationally expensive ingredients in density functional approximations for Kohn-Sham density functional theory. We present detailed tests of some exact nonempirical upper bounds to exact exchange. These "Rung 3.5" upper bounds contract the Kohn-Sham one-particle density matrix with model density matrices used to construct semilocal model exchange holes and invoke the Cauchy-Schwarz inequality. The contraction automatically eliminates the computationally expensive long-range component of the exact exchange hole. Numerical tests show that the exchange upper bounds underestimate total exchange energies while predicting other properties with accuracy approaching standard hybrid approximations.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Christian University , Fort Worth, Texas 76110, United States.
authors.forename: Emil
authors.identifier: http://orcid.org/0000-0002-1141-241X
authors.initials: E
authors.lastname: Proynov
authors.affiliation: Department of Chemistry and Biochemistry, Texas Christian University , Fort Worth, Texas 76110, United States.
authors.forename: Benjamin G
authors.identifier: http://orcid.org/0000-0002-2572-5273
authors.initials: BG
authors.lastname: Janesko