O.B.Spirina, N.V.Shokhirev
Semi-Empirical Method For Calculation of Potential Surfaces of Radical
Reactions of CH4 + CH.3 -->
CH.3 + CH4 In The Basis of Boundary
Orbitals
Teoreticheskaya I Eksperimentalnaya Khimiya. 27:(4) 499-506, 1991
Abstract:
A semiempirical approach in terms of the ZDO method is suggested to
described potential energy surface (PES) of some radical reactions with a
bounded basis including only frontier (single-filled) molecular orbitals
of radicals depending on the geometric parameters with allowance for all
the possible configuration. The methods for a choice of parameters are
analyzed. The developed approach has been used to calculate the PES of
CH4 + CH.3 --> CH.3 +
CH4 reaction some points of which are checked up by the nonempiric
method allowing for correlation energy according to perturbation theory.
Relaxation energies are calculated. One-site parameters are found from
the nonempiric consideration of CH3+, CH3 and
CH3- energy, two-site ones - from simulation of
CH4 ® CH3 + H and
C2H6 ® 2CH3
reactions in terms of the same one-orbital approximation. Energy parameters of
the considered reactions are over-estimated by 10% while geometric ones - by 15%.
The Hartree-Fock solutions and the solutions allowing for Cl have been also
comparatively analyzed; the changes in spin and charge densities on the
reaction centers have been considered.