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Unrestricted hartree‐fock SCF calculations on some hypothetical molecules with triplet ground states
Author(s) -
Phillips Donald H.,
Schug John C.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560050724
Subject(s) - hartree–fock method , ground state , molecule , chemistry , computational chemistry , physics , atomic physics , quantum mechanics
Semi‐empirical restricted Hartree–Fock calculations including limited configuration interaction predict negative excitation energies for transitions from the conventional singlet ground state to the lowest triplet state of some hypothetical photo‐products of dipyridine‐glyoxal and bianthrone. This result is also obtained for the molecule dichlorodioxazine. Unrestricted (different orbitals for different spins) semi‐empirical calculations also result in the prediction of triplet ground states. Further calculations on molecules which are analogs of the hypothetical product from dipyridine‐glyoxal indicate that the prediction of a triplet ground state hinges upon a subtle balance of the changes in the expectation values of the exchange, coulomb and core energies in going to triplet state. The presence of hetero atoms and the number of pi electrons have large effects on this balance.