title: Revisiting Molecular Dissociation in Density Functional Theory: A Simple Model.
abstract: A two-electron one-dimensional model of a heteroatomic molecule composed of two open-shell atoms is considered. Including only two electrons isolates and examines the effect that the highest occupied molecular orbital has on the Kohn-Sham potential as the molecule dissociates. We reproduce the characteristic step and peak that previous high-level wave function methods have shown to exist for real molecules in the low-density internuclear region. The simplicity of our model enables us to investigate in detail their development as a function of bond-length, with little computational effort, and derive properties of their features in the dissociation limit. We show that the onset of the step is coincident with the internuclear separation at which an avoided crossing between the ground-state and lowest charge-transfer excited-state is approached. Although the step and peak features have little effect on the ground-state energetics, we discuss their important consequences for dynamics and response.
authors.affiliation: Department of Physics and Astronomy, Hunter College and City University of New York, 695 Park Avenue, New York, New York 10065, and Department of Chemistry and The Beckman Institute, University of Illinois, Urbana, Illinois 61801.
authors.forename: David G
authors.initials: DG
authors.lastname: Tempel
authors.affiliation: Department of Physics and Astronomy, Hunter College and City University of New York, 695 Park Avenue, New York, New York 10065, and Department of Chemistry and The Beckman Institute, University of Illinois, Urbana, Illinois 61801.
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Martínez
authors.affiliation: Department of Physics and Astronomy, Hunter College and City University of New York, 695 Park Avenue, New York, New York 10065, and Department of Chemistry and The Beckman Institute, University of Illinois, Urbana, Illinois 61801.
authors.forename: Neepa T
authors.initials: NT
authors.lastname: Maitra