Alternant orbitals method

Itoh, T., and Yoshizumi, H., J. Phys. Soc. Japan 10. 201, "Application of the alternant orbital method to benzene." Construction of a determinant using the semilocalized MO and selection of the singlet component of it. 

Yoshizumi, H., and Itoh, T., J. Chem. Phys. 23, 412, "Applications of the alternant molecular orbital method to six and four electron systems."... 

It is also possible to employ highly correlated reference states as an alternative to methods that employ Hartree-Fock orbitals. Multiconfigu-rational, spin-tensor, electron propagator theory adopts multiconfigura-tional, self-consistent-field reference states [37], Perturbative corrections to these reference states have been introduced recently [38],... 

Abstract A mixed molecular orbital and valence bond (MOVE) method has been developed and applied to chemical reactions. In the MOVE method, a diabatic or valence bond (VE) state is defined with a block-localized wave function (ELW). Consequently, the adiabatic state can be described by the superposition of a set of critical adiabatic states. Test cases indicate the method is a viable alternative to the empirical valence bond (EVE) approach for defining solvent reaction coordinate in the combined qnantum mechanical and molecnlar mechanical (QM/MM) simulations employing exphcit molecular orbital methods. 

J.-L. Calais, Abstracts of Uppsala Dissertations in Science 52 ( 1965 ), R. Pauncz, Alternant Molecular Orbital Method ( W. B. Saunders, Philadelphia 1967 )... 

Nevertheless, acknowledging or denying the existence of differences between resonance theory and classical structural theory was dependent on their different assessments of the role of alternative methods to study molecular structure. Wheland equated resonance theory to the valence bond method and viewed them as alternatives to the molecular orbital method. Pauling conceded that the valence bond method could be compared with the molecular orbital method, but not with... 

For direct Af-electron variational methods, the computational effort increases so rapidly with increasing N that alternative simplified methods must be used for calculations of the electronic structure of large molecules and solids. Especially for calculations of the electronic energy levels of solids (energy-band structure), the methodology of choice is that of independent-electron models, usually in the framework of density functional theory [189, 321, 90], When restricted to local potentials, as in the local-density approximation (LDA), this is a valid variational theory for any A-electron system. It can readily be applied to heavy atoms by relativistic or semirelativistic modification of the kinetic energy operator in the orbital Kohn-Sham equations [229, 384],... 

Ruben Pauncz, Studies in Physics and Chemistry, No. 4. Alternant Molecular Orbital Method, Saunders, Philadelphia, 1967. 

Kenichi Fukui and Roald Hoffmann won the Nobel prize in 1981 (Woodward died in 1979 and so couldn t share this prize he had already won the Nobel prize in 1965 for his work on synthesis) for the application of orbital symmetry to pericyclic reactions. Theirs is an alternative description to the frontier orbital method we have used and you need to know a little about it. They considered a more fundamental correlation between the symmetry of all the orbitals in the starting materials and all the orbitals in the products. This is rather too complex for our consideration here, and we shall concentrate only on a summary of the conclusions—the Woodward-Hoffmann rules. The most important of these states ... 

Pauncz, R. Alternant Molecular Orbital Method, Philadelphia Saunders 1967. 3°) Empedocles, D. D., Linnett, J. W. Theoret. Chim. Acta 4, 377 (1966) Proc. 

Rat IV Route. Groups of 12 Fisher 344N rats of both sexes (13A2 weeks old) shall be dosed intravenously with a test chemical IV formulation at one dose (2.5 mg/kg). Blood samples shall be taken at eight time points (to be determined based on the results of the preliminary study) after IV administration, with three animals bled at each time point. Two blood samples at different times (preferably >2 hr apart) shall be collected via alternating orbital sinuses from each dosed rat. Test chemical concentrations shall be determined in plasma using a validated analytical method. 

Groups of nine mice of each sex shall be added to each dose group of the chronic study. No control mice are needed for this study. Blood samples shall be collected only at 12 months with three mice being bled at each of six time points (to be determined based on the singleadministration study). Each mouse shall be sampled twice via alternating orbital sinuses at different times (preferably >2 hr apart). After sampling, mice shall be sacrificed. Blood concentrations of decalin/tetralin shall be determined using the validated analytical method. 

The scientifically orthodox resolution of this difficulty is spelled out in many places (e.g., McWeeny, 1979, ch. 5). MO and VB theories are shown to be alternative first steps in a pair of schemes designed to successively approximate to an accurate quantum mechanical solution for the structure of a molecule. One aspect of this process that makes it seem a little less convincing is that the later steps in the approximation schemes differ markedly from the first. For example, with MO theory, a series of MO-Uke steps of successive approximation leads not to an accurate solution of the equations that arise from quantum theory but to the Hartree Fock limit. It is only by taking a rather different type of step, quite out of tune with the basis of the molecular orbital method—configuration interaction or some alternative—that the quantum theory solution can be approximated. 

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