Multiconfiguration wavefuntions for the lowest (ππ*) excited states of ethylene
Charles F. Bender, Thom H. Dunning Jr., Henry F., III Schaefer, William A. Goddard III, William J. Hunt
Abstract
Ab initio calculations have been carried out for the T(^(3)B_(1u)) and V(^(1)B_(1u)) states of ethylene in a planar nuclear configuration. A "double-zeta" gaussian basis, augmented by diffuse functions, was used. A wide variety of configuration interaction wavefunctions (including as many as 1605 configurations), optimized by the iterative natural orbital method, were computed. The calculations predict the ^(1)B_(1u) state to lie 3.8 – 4.1 eV above the 3B1u state. The spatial extent of the triplet state is that of a normal valence state with (x2) ≈ 12 bohr^2. The singlet state, on the other hand, is found to be quite diffuse or Rydberg-like, (x^2) ≈ 35 bohr^2; electron correlation was found to decrease (x^2) by 30% from the Hartree - Fock value (52 bohr^2). This result is not consistent with simple notions concerning π-electron theory.
Group Members
Bender, C. F., Jr., T. H. D., Schaefer, H. F. I., III, W. A. G., & Hunt, W. J. (1972). Multiconfiguration wavefuntions for the lowest (ππ*) excited states of ethylene. *Chem. Phys. Lett.*, *15*(2), 171-178. https://doi.org/10.1016/0009-2614(72)80143-X