A complete active space valence bond (CASVB) method

Hirao, Kimihiko; Nakano, Haruyuki; Nakayama, Kenichi; Dupuis, Michel
November 1996
Journal of Chemical Physics;11/22/1996, Vol. 105 Issue 20, p9227
Academic Journal
A complete active space valence bond (CASVB) method is proposed which is particularly adapted to chemical interpretation. A CASVB wave function can be obtained simply by transforming a canonical CASSCF function and readily interpreted in terms of the well known classical VB resonance structures. The method is applied to the ground and excited states of benzene, butadiene, and the ground state of methane. The CASVB affords a clear view of the wave functions for the various states. The electronic excitation is represented in a VB picture as rearrangements of the spin couplings or as charge transfers which involve breaking covalent bonds and forming new ionic bonds. The former gives rise to covalent excited states and the latter to ionic excited states. The physical reasons why it is so difficult to describe the ionic excited states at the CASSCF level with a single active space and why the lowest 1 1B+2 state in cis-butadiene is so stabilized compared to the corresponding 1 1B+u state in the trans isomer are easily identified in view of a VB picture. The CASVB forms a useful bridge from molecular orbital theory to the familiar concepts of chemists. © 1996 American Institute of Physics.


Related Articles

  • The valence band structures of BeO, MgO, and CaO. Sashin, Vladimir A.; Dorsett, Helen E.; Bolorizadeh, Mohammad A.; Ford, Michael J. // Journal of Chemical Physics;11/8/2000, Vol. 113 Issue 18 

    We have performed direct measurements of the valence band structures of the light alkaline earth oxides BeO, MgO, and CaO using electron momentum spectroscopy (EMS). From these measurements, we have determined the band dispersions, valence bandwidths, and O(2s)-O(2p) intervalence bandgaps at the...

  • Impurity bands and band tailing in moderately doped silicon. Lowney, Jeremiah R. // Journal of Applied Physics;3/15/1986, Vol. 59 Issue 6, p2048 

    Presents a study which calculated the density states of the valence and conduction bands in moderately doped silicon. Theory; Results and discussion; Conclusions.

  • Resonant tunneling of holes in Si/GexSi1-x. Fu, Y.; Chen, Q.; Willander, M. // Journal of Applied Physics;12/15/1991, Vol. 70 Issue 12, p7468 

    Reports on the effects of strains on the band structures by calculating the valence bands of bulk silicon (Si), unrelaxed Si grown on Ge[subx]Si[sub1-x], bulk Ge[subx]Si[sub1-x] and unrelaxed Ge[subx]Si[sub1-x] grown on Si. Theory behind the band structures; Data on the tunneling current...

  • Absence of charge fluctuations of europium in metallic single crystals of EuCu2Si2. Stadnik, Z. M.; Wang, P.; Żukrowski, J.; Cho, B. K. // Hyperfine Interactions;2006, Vol. 169 Issue 1-3, p1295 

    The 151Eu Mössbauer effect study in the temperature range 2.2–299.5 K on pulverized single crystals of EuCu2Si2 synthesized from an indium flux is presented. In contrast to previous studies on polycrystalline samples in which valence fluctuations for Eu were reported, we find that the...

  • Energy Band Genesis from Sublattice States in Sulfides of Alkali Metals with an Antifluorite Lattice. Zhuravlev, Yu. N.; Kosobutskii, A. B.; Poplavnoi, A. S. // Russian Physics Journal;Feb2005, Vol. 48 Issue 2, p138 

    Based on the density functional, self-consistent band spectra from crystals and charged sublattices of alkali metal sulfides are calculated by the method of pseudopotential in the basis of localized orbitals. Different charge states of sublattices compatible with the electric neutrality of...


    In analogy to the analysis of minimal conditions for the formation of diffusion driven instabilities in the sense of Turing, in this paper minimal conditions for a class of kinetic equations with mass conservation are discussed, whose solutions show patterns with a characteristic wavelength. The...

  • x-dependence of the quark distribution functions in the χCQMconfig. Dahiya, H.; Gupta, M. // European Physical Journal C -- Particles & Fields;Nov2007, Vol. 52 Issue 3, p571 

    Chiral constituent quark model with configuration mixing (χCQMconfig) is known to provide a satisfactory explanation of the “proton spin problem” and related issues. In order to enlarge the scope of χCQMconfig, we have attempted to phenomenologically incorporate x-dependence...

  • Mechanically Induced Reduction of Europium(III). Kazakov, V. P.; Ostakhov, S. S.; Alyab'ev, A. S.; Shishlov, N. M. // High Energy Chemistry;Mar/Apr2003, Vol. 37 Issue 2, p121 

    Examines the feasibility of mechanically induced valence transitions in the crystal hydrate of europium (III) oxide. Method of initiating valence transitions of solid materials; Relevance of the appearance of an EPR signal to the mechanical reduction of europium; Valence transition process of...

  • Ab initio study of AmCl+: f–f spectroscopy and chemical binding. Tilson, Jeffrey L.; Naleway, Conrad; Seth, Michael; Shepard, Ron; Wagner, Albert F.; Ermler, Walter C. // Journal of Chemical Physics;9/22/2004, Vol. 121 Issue 12, p5661 

    A valence full configuration interaction study with a polarized double-ζ quality basis set has been carried out for the lowest 49 electronic states of AmCl+. The calculations use a pseudopotential treatment for the core electrons and incorporate a one-electron spin–orbit interaction...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics