Acta Phys. -Chim. Sin. ›› 1986, Vol. 2 ›› Issue (03): 249-253.doi: 10.3866/PKU.WHXB19860310

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ab initio CALCULATIONS OF EQUILIBRIUM GEOMETRY AND HYPERFINE COUPLING CONSTANTS OF CATION CH2CO+

Yu Jianguo; Huang Mingbao; Liu Ruozhuang   

  1. Quantum Chemistry Group, Dept. of Chemistry, Beijing Normal University; Dept. of Modern Chemistry, University of Science and Technology of China
  • Received:1985-05-21 Revised:1985-12-23 Published:1986-06-15

Abstract: The equilibrium geometry and hyperfine coupling constants of cation CH_2CO~+ have been calculated by the UHF method, within the ab initio MO LCAO SCF approximation. The minimal basis set STO-3G was used. The ground state of this cation is ~2B_1 and it is a π-radical. Compared with its neutral parent molecule, the cation has a markedly long C=C bond (0.14138 nm) and a slightly short C=O bond (0.11738 nm), which have been explained by raeans of the analysis of their electronic structures.
Based on the theory of Amos and Snyder, annihilation of the quartet contamination in the UHF wavefunction results in an approximate pure doublet wavefunction. The isotropic hyperfine coupling constants a_H of cation CH_2CO~+ were evaluated from both the spin densities without and with quartet annihilation, which are 49.9G and 16.3G, respectively. The latter one is close to the experimental value (≈20G).