Characteristics of the calculations for molecules with a partially filled pair of degenerate molecular orbitals in the restricted Hartree-Fock approximation using the MINDO/3 method. Monocyclic antiaromatic polymethynes (CH)/sub n/

In calculations for molecules with a partially filled pair of degenerate MO's in the restricted Hartree-Fock approximation, within the framework of the one-determinant scheme, an incorrect initial filling will lead to solutions with artifact character which do not correspond to a stationary point on the potential energy surface. In their work they have considered as an example the calculations using the MINDO/3 method; but it is obvious that ignoring the methodological problem of the initial filling leads to an incorrect result even when they use different calculation methods. As a consequence of this, they give results of calculations for cyclobutadiene using the PPP method, according to which the energy difference between the singlet and triplet states for the D/sub 4h/ structure is equal to 60.2 kJ/mole