Author:
Holka Filip,Neogrády Pavel,Urban Miroslav,Paldus Josef
Abstract
We study the effect of a confining potential on systems that exhibit Hartree-Fock (HF) instabilities, and thus admit broken symmetry (BS) HF solutions, by relying on the O2- and S2- doubly-charged anions as model systems. We find that with the increasing strength of the external harmonic confinement potential, W(r) = 1/2(ωr)2 (with 0.0 ≤ ω < 0.2), the BS solutions are systematically eliminated. We use extended, diffuse, doubly-augmented Gaussian basis sets up to and including d-aug-cc-pV6Z, and find that the number and the character of BS solutions exhibit significant basis set effects. These basis sets were further extended by additional ghost basis functions, located away from the atomic center. The role of the electron correlation effects for the BS HF solutions was examined by the CCSD(T) method. In addition to modelling the confinement by the harmonic-like potential W(r), we also examined a more realistic "confinement", realized by a grid of point charges modelling the crystal structure of MgO. Again, we find that the HF instabilities and the implied BS solutions disappear with the increasing magnitude of the model charges simulating the crystal environment. At the same time, the O2- anion is energetically stabilized with respect to both the O- anion and the neutral oxygen atom.
Publisher
Institute of Organic Chemistry & Biochemistry
Cited by
10 articles.
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