title: Visualization and analysis of the Kohn-Sham kinetic energy density and its orbital-free description in molecules.
abstract: We visualize the Kohn-Sham kinetic energy density (KED) and the ingredients--the electron density, its gradient, and Laplacian--used to construct orbital-free models of it, for the AE6 test set of molecules. These are compared to related quantities used in metaGGA's, to characterize two important limits--the gradient expansion and the localized-electron limit typified by the covalent bond. We find the second-order gradient expansion of the KED to be a surprisingly successful predictor of the exact KED, particularly at low densities where this approximation fails for exchange. This contradicts the conjointness conjecture that the optimal enhancement factors for orbital-free kinetic and exchange energy functionals are closely similar in form. In addition we find significant problems with a recent metaGGA-level orbital-free KED, especially for regions of strong electron localization. We define an orbital-free description of electron localization and a revised metaGGA that improves upon atomization energies significantly.
authors.affiliation: Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306, USA.
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Cancio
authors.affiliation: Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306, USA.
authors.forename: Dane
authors.initials: D
authors.lastname: Stewart
authors.affiliation: Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306, USA.
authors.forename: Aeryk
authors.initials: A
authors.lastname: Kuna