UHF-MINDO/3 study of the thermally forbidden dissociation of o,o'-dibenzene in two benzene molecules : Part 1. Description of the postulated diradical intermediate

• Published in: Journal of molecular structure. Theochem 1992-12, Vol.277, p.15-29
• Main Authors: Cometta-Morini, Chiara, Baumann, Harold, Oth, Jean F.M.
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Physics; Semi-empirical and empirical calculations (differential overlap, hückel, ppp methods, etc.)
• ISSN: 0166-1280; 1872-7999
• DOI: 10.1016/0166-1280(92)87126-K

The single-determinant UHF-MINDO/3 method has been used for the description of the supposed diradical intermediate in the thermally forbidden dissociation of o,o'-dibenzene into two benzene molecules. The results of the UHF-MINDO/3 computations have been compared with those of CI-MINDO/3 calculations. The stability of the restricted Hartree-Fock (RHF) solution has been investigated and the relationship between instability and onset of diradical character discussed. The UHF-MINDO/3 method has been found to be adequate to describe well the electronic distribution in the diradical intermediate. The spin annihilation method, which has been used as a first attempt in solving the problem of spin contamination, has proven inadequate. Consequently a better spin projection technique is required.