Topography of potential energy surfaces
The curves on a multi—dimensional potential energy iuCace (PES) linking the reactant and the transition state configurations are constructed. They are generally distinct frOm usual reaction path curves and a special term "optimum ascent path" (oAF) is accepted for them. A local criterion is formulated allowing to distinguish the points located on an OAP among other points in its vicinity. A mathematical analysis of singular points of a PES, where its valleys or ridges emerge, dissipate or bifurcate, is presented. These points are specified as different branching points of OAPs.