Articles you may be interested inA fusion of the closed-shell coupled cluster singles and doubles method and valence-bond theory for bond breaking Electron density, exchange-correlation density, and bond characterization from the perspective of the valence-bond theory. I. Two simple analytical cases and, if estimates of the a. are available, B. and the equilibrium geometry follow. a2 and a4 were determined in this work (a2 for 'OBF 3 =-0.OOO17 cm-I, a4 for IOBF 3 = -0.00063 cm-I ). We have previously found that al=0.0008 cm-1 (Ref. 4) and a3=0.0015 cm-I.14 These 14 C. W. Brown and J. Overend (to be published). values, with Eq. (7) lead to a value of B.=0.345 9 ± 0.001 cm-I, corresponding to an equilibrium BF bond length r.= 1.307±0.002 A.Valence-bond (VB) theory is formulated in a general form, to be applied to states of any multiplicity, with inclusion of both spin and orbital degeneracy. Structures are related to products of spin functions, the leading terms, and a one-to-one correspondence is established between these products and extended Rumer diagrams. A relationship is also found with genealogical spin functions. The leading terms can be directly used in the calculation of energy eigenvalues and eigenvectors. Applications to simple hydrocarbon systems are shown, and the results are compared with experimental data.
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