Reassessing Spin-Coupled (Full Generalized Valence Bond) Descriptions of Ozone Using Three-Center Bond Indices.

0480523 - ÚCHP 2018 RIV NL eng J - Článek v odborném periodiku
Cooper, D.L. - Penotti, F.E. - Ponec, Robert
Reassessing Spin-Coupled (Full Generalized Valence Bond) Descriptions of Ozone Using Three-Center Bond Indices.
Computational and Theoretical Chemistry. Roč. 1116, Sl (2017), s. 40-49. ISSN 2210-271X. E-ISSN 1872-7999
Institucionální podpora: RVO:67985858
Klíčová slova: full GVB and spin-coupled * PI-system in O3 * domain-averaged fermi holes
Obor OECD: Physical chemistry
Impakt faktor: 1.443, rok: 2017

Domain-averaged Fermi hole analysis is carried out for the ground state of O3 at its equilibrium geometry using a complete-active-space self-consistent field CASSCF(18,14) wavefunction, based on a slightly expanded full-valence active space. This initial analysis is augmented with an examination of the corresponding localized natural orbitals (LNOs) and of the numerical values obtained with a new improved definition of three-center bond indices for correlated singlet systems. Much the same pattern of LNOs is observed when using instead a subsequent internally-contracted multiconfiguration-reference configuration interaction construction, which also provides very similar values for the three-center bond indices. This gives us confidence to use such bond indices, alongside relative energies and the electric dipole moment, to assess the relative merits of various combinations of spin-coupled (full generalized valence bond) components with ten active electrons: four π, four σ bonding and the two nonbonding σ electrons associated with the central O atom. These multi-component valence bond descriptions were generated either with or without subsequent orbital reoptimization. The description of the π system which emerges from all of our analysis conforms to a standard model of three-center four-electron π bonding that incorporates a nontrivial degree of (partial) diradical character. Whereas certain combinations of ten-electron spin-coupled components can faithfully reproduce such a picture, none of the individual rival components appears to have sufficient flexibility on its own.
Trvalý link: http://hdl.handle.net/11104/0276291