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

摘要

In the present work 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 bassi set on the lowest A_1,B_1,A_2,and B_2 doublet and quartet potential energy sufaces (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 NO_2(~2A_1),MIN2(~2B-2),NO_2(~2II_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.,~2B_2/~2A_1) has been previously reportdin theoretical and experimental studies.High-energy barriers were found for thedirect 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.