The lowest doublet and quartet potential energy surfaces involved in the N(S-4)+O-2 reaction. II. Ab initio study of the C-2v-symmetry insertion mechanism

摘要

In the present work we have carried out ab initio complete active space self-consistent field (CASSCF) and second-order perturbation theory on CASSCF wave function (CASPT2) calculations and also some density functional theory calculations with the aug-cc-pVTZ Dunning's basis set on the lowest A(1), B-1, A(2), and B-2 doublet and quartet potential energy surfaces (PES) that could be involved in the title reaction. Thus, several minima, transition states, and surface crossings have been found for the C-2v-insertion reaction mechanism. The results agree very well with available experimental data [i.e., for NO2 ((2)A(1)), MIN2 (B-2(2)), NO2 ((2)Pi(u))] and with other previous ab initio calculations. Six A'/A'- and four A'/A'-type surface crossings were located and classified for these PES', whose only one (i.e., B-2(2)/(2)A(1)) has been previously reported in theoretical and experimental studies. High-energy barriers were found for the direct C-2v-insertion mechanism (3.11 and 2.54 eV for the lowest doublet and quartet PES' at the CASPT2/aug-cc-pVTZ level, respectively), clearly showing that this competitive mechanism is much less favorable than the direct C-s-abstraction or the indirect C-s-insertion reaction mechanisms reported in Paper I. (C) 2002 American Institute of Physics. [References: 49]