Dissociation of diatomic molecules and the exact-exchange Kohn-Sham potential: The case of LiF

Journal Article · Wed Jun 15 04:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.062512· OSTI ID:21550101

Makmal, Adi; Kronik, Leeor ^[1]; Kuemmel, Stephan ^[2]

---

1. Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)
2. Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany)

We examine the role of the exact-exchange (EXX) Kohn-Sham potential in curing the problem of fractional molecular dissociation. This is achieved by performing EXX calculations for the illustrative case of the LiF molecule. We show that by choosing the lowest-energy electronic configuration for each interatomic distance, a qualitatively correct binding energy curve, reflecting integer dissociation, is obtained. Surprisingly, for LiF this comes at the cost of violating the Aufbau principle, a phenomenon we discuss at length. Furthermore, we numerically confirm that in the EXX potential of the diatomic molecule, one of the atomic potentials is shifted by a constant while the other one is not, depending on where the highest occupied molecular orbital is localized. This changes the relative positions of the energies of each atom and enforces the integer configuration by preventing spurious charge transfer. The size of the constant shift becomes increasingly unstable numerically the larger the interatomic separation is, reflecting the increasing absence of coupling between the atoms.

• OSTI ID: 21550101
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 6 Vol. 83; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METAL COMPOUNDS
ATOMS
AUFBAU PRINCIPLE
BINDING ENERGY
CALCULATION METHODS
COUPLING
DISSOCIATION
DISTANCE
ELECTRONIC STRUCTURE
ENERGY
EXCHANGE INTERACTIONS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
INTERACTIONS
INTERATOMIC DISTANCES
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
MOLECULAR ORBITAL METHOD
MOLECULES
POTENTIALS