A molecular-orbital theoretical classification of reactions of singlet ground-state molecules
TL;DR: In this article, the reaction mechanisms of molecular systems in the ground singlet state are discriminated with the triplet stability-instability criterion of restricted Hartree-Fock (RHF) solution for the entire system and with the phase continuity criterion of the highest occupied orbital involved.
About: This article is published in Chemical Physics Letters.The article was published on 1973-10-15. It has received 109 citations till now. The article focuses on the topics: Singlet state & Molecular orbital.
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270 citations
TL;DR: In this article, full configuration interaction in the space of fractionally occupied unrestricted Hartree-Fock natural orbitals is proposed as an inexpensive alternative to the complete active space-consistent field method for ground states.
Abstract: Full configuration interaction in the space of fractionally occupied unrestricted Hartree–Fock natural orbitals is proposed as an inexpensive alternative to the complete active space–self‐consistent‐field method for ground states. In most cases, this method requires only a fraction of the computational effort of the latter and gives comparable results, as demonstrated on several examples. Gradient evaluation, while more complex in formulation, is computationally not significantly more expensive than unrestricted Hartree–Fock gradients.
204 citations
TL;DR: In this article, the roles of orbital, spin and permutation symmetries in the extended Hartree-Fock (EHF) wavefunction are investigated in relation to the applications of group theory to chemical reactions.
Abstract: The roles of orbital, spin and permutation symmetries in the extended Hartree-Fock (EHF) wavefunction are investigated in relation to the applications of group theory to chemical reactions. The utility of the magnetically ordered set for an extended HF calculation is pointed out. The relative stabilities among linear Huckel and Mobius three-center three-electron (3,3) systems are investigated by the generalized Hartree-Fock (GHF) and EHF methods in order to confirm the reliability of the valence-bond (VB) selection rule for free radical reactions.
194 citations
TL;DR: In this paper, a generalized molecular orbital (GMO) theory for magnetically interacting organic compounds has been presented and applied to the calculations of the effective exchange integrals (Jab) for the cyclophane-type carbene dimers whose para and ortho-isomers have the high-spin ground state.
Abstract: A generalized molecular orbital (GMO) theory for magnetically interacting organic compounds has been presented. The theory is applied to the calculations of the effective exchange integrals (Jab) for the cyclophane-type carbene dimers whose para and ortho-isomers have the high-spin ground state. The calculated Jab-values are consistent with observations.
175 citations
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TL;DR: In this paper, the stability conditions for the solutions of the Hartree-Fock equations for the simple open-shell case, i.e., closed shell with one extra electron, are derived.
Abstract: The stability conditions for the solutions of the Hartree–Fock equations for the simple open‐shell case, i.e., closed shell with one extra electron, are derived. It is shown that only “doublet stability” is relevant is this simple open‐shell case, the solutions being always “nondoublet unstable.” The doublet stability conditions are then derived using the mathematical methods of quantum field theory, namely, occupation number representation, Wick's theorem, and Feynman‐like diagrams. In order to familiarize the reader with the use of these concepts they are first used to rederive the singlet and nonsinglet stability conditions for the closed‐shell case. A general method of finding new Hartree–Fock solutions, in the case that the symmetry adapted Hartree–Fock solutions are unstable, is briefly discussed. The implications of the instability on the ground‐state correlation energy calculations and on the excitation energy calculations using time‐dependent Hartree–Fock theory are considered.
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