Abstract
The ground state energies of CH +3 , CH3, and CH −3 are calculated both in the SCF (near Hartree-Fock) approximation and in the IEPA-PNO scheme including correlation energy. Due to a more appropriate choice of the basis, our SCF-values for CH −3 are substantially better than previously published ones. Both CH +3 and CH3 are planar whereas the equilibrium bond angles in CH −3 are nearly tetrahedral. The inversion barrier of CH −3 is ∼ 2kcal/mol. The force constants of the out-of-plane bending modes are changed by correlation in the case of CH3 from 0.03–1.8 mdyn/Å. The localized MO's that correspond to the CH-bonds are “bent” in the non-equilibrium geometries. The dependence of the different pair correlation contributions on the angle γ that describes out-of-plane deformation is analyzed. The electron affinity of CH3 is ∼0.3 eV. Finally the Pariser-Parr disproportionation reaction is analyzed in the light of the present results. Changes in correlation energy for this reaction amount to less than 1 eV.
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Driessler, F., Ahlrichs, R., Staemmler, V. et al. Ab-initio calculations on small hydrides including electron correlation. Theoret. Chim. Acta 30, 315–326 (1973). https://doi.org/10.1007/BF00527465
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DOI: https://doi.org/10.1007/BF00527465
