Capability of LEP-type surfaces to describe noncollinear reactions.: 2.: Polyatomic systems

In this second article of the series, the popular LEP-type surface for collinear reaction paths and a "bent" surface, which involves a saddle point geometry with a nonlinear central angle, were used to examine the capacity of LEP-type surfaces to describe the kinetics and dynamics of noncollinear reaction paths in polyatomic systems. Analyzing the geometries, vibrational frequencies, curvature along the reaction path (to estimate the tunneling effect and the reaction coordinate-bound modes coupling), and the variational transition-state theory thermal rate constants for the NH3 + O(P-3) reaction, we found that the "collinear" LEP-type and the "bent" surfaces for this polyatomic system show similar behavior, thus allowing a considerable saving in time and computational effort. This agreement is especially encouraging for this polyatomic system because in the Cs symmetry the reaction proceeds via two electronic states of symmetries (3)A' and (3)A". which had to be independently calibrated. Finally, this work on polyatomic systems generalizes the conclusions reached in our previous article on triatomic systems, so that it therefore appears to be a general behavior for any reactive system.