EXTENSIVE AB-INITIO STUDY OF THE OH- LOW-LYING ELECTRONIC STATES OF THE STATIONARY-POINTS ON THE (2)A' SURFACE(HCN REACTION )

We found many stationary points (minima and transition states) for the title reaction on the (2)A' surface at unrestricted Hartree-Fock self -consistent field (UHF-SCF) level with two different basis sets. Stabl e adducts, as suggested by previous experimental works, have been asce rtained and several reaction paths are obtained through intrinsic reac tion coordinate (IRC) calculations. A link to the HNC+OH reaction is p ossible. Multiconfiguration SCF (MC-SCF) calculations have been carrie d out for the addition reaction with the lowest energy barrier in orde r to eliminate the spin contamination error on these geometries. Corre lation energy at the stationary points was estimated via a perturbativ e scheme, Moller-Plesset at fourth order (MP4) which does not seem ade quate for such a system, and via multireference double configuration i nteraction (MR-DCI) with extrapolation to full CI values for ground an d first excited states. Electronic excitations may open some reaction channels. (C) 1996 American Institute of Physics.