Abstract
A semiempirical approach is suggested to describe potential-energy surfaces (PESs) of some radical reactions in the zero-differential overlap (ZDO) approximation. An incomplete basis set is used including only frontier (single-filled) radical molecular orbitals (MOs) depending on geometrical parameters. All possible configurations are taken into account. The parameter selection techniques are analyzed. The approach is applied to PES calculation of the CH4 + CH3 · → CH3 · + CH4 reaction. Some points of the PES are verified by a nonempirical method using the perturbation theory and taking into account the correlation energy. The relaxation energies are calculated. The one-center parameters are determined nonempirically from the CH3 + CH3 ·, and CH3 − energetics. The two-center parameters are found by modeling the CH4 → CH3 · + H and C2H6 → 2CH3 reactions in the same single-orbital approximation. The energy parameters of the reactions considered are overestimated by 10%, whereas the geometrical parameters are under-estimated by 15%. Further, a comparative analysis of the Hartree-Fock solutions and those including correlation interactions (CIs) is given. The variations in the spin and charge densities on the reaction centers are considered.
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Additional information
Institute of Chemical Kinetics and Combustion, Academy of Sciences of the USSR, Siberian Branch, Novosibirsk. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 499–506, July–August, 1991. Original article submitted February 10, 1989.
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Spirina, O.B., Shokhirev, N.V. Semiempirical calculation of the CH4 + CH3 · → CH3 · + CH4 radical-reaction potential surfaces in a basis of frontier orbitals. Theor Exp Chem 27, 437–442 (1991). https://doi.org/10.1007/BF01372526
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DOI: https://doi.org/10.1007/BF01372526