Electronic symmetry breaking in polyatomic molecules. Multiconfiguration self-consistent field study of the cyclopropenyl radical C/sub 3/H/sub 3/

Journal Article · Sun Jan 01 04:00:00 EST 1984 · J. Chem. Phys.; (United States)

OSTI ID:5457836

Hoffmann, M R; Laidig, W D; Kim, K S; Fox, D J; Schaefer, III, H F

For equilateral triangle geometries (point group D/sub 3h/), the C/sub 3/H/sub 3/ radical has a degenerate /sup 2/E'' electronic ground state. Although the /sup 2/A/sub 2/ and /sup 2/B/sub 1/ components separate in energy for C/sub 2v/ geometries, these two components should have identical energies for equilateral triangle structures. In fact, when approximate wave functions are used and the orbitals not required to transform according to the D/sub 3h/ irreducible representations, an energy separation between the /sup 2/A/sub 2/ and /sup 2/B/sub 1/ components is observed. At the single configuration self-consistent field (SCF) level of theory this separation is 2.8 kcal with a double-zeta basis set and 2.4 kcal with double-zeta plus polarization. It has been demonstrated that this spurious separation may be greatly reduced using multiconfiguration self-consistent field (up to 7474 variationally optimum configurations) and configuration interaction (up to 60 685 space and spin adapted configurations) techniques. Configurations differing by three and four electrons from the Hartree--Fock reference function are found necessary to reduce the /sup 2/A/sub 2/-/sup 2/B/sub 1/ separation to below 0.5 kcal.

• Research Organization: Department of Chemistry and Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
• OSTI ID: 5457836
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 80:1; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
CONFIGURATION INTERACTION
ELECTRONIC STRUCTURE
FUNCTIONS
HYDROCARBONS
ORGANIC COMPOUNDS
RADICALS
SELF-CONSISTENT FIELD
WAVE FUNCTIONS