Crossing seams, energy surfaces

Here the transition state is approximated by the lowest crossing pomt on the seam intersecting the diabatic (non-interacting) potential energy surfaces of the reactant and product. The method was originally developed... 

Koga N and Morokuma K 1985 Determination of the lowest energy point on the crossing seam between two potential surfaces using the energy gradient Chem. Phys. Lett. 119 371... 

A and A = 0.1 eV. The adiabatic ground potential energy surface is shown in Fig. 11. The present results (solid line) are in good agreement with the quantum mechanical ones (solid circles). The minimum energy crossing point (MECP) is conventionally used as the transition state and the transition probability is represented by the value at this point. This is called the MECP approximation and does not work well, as seen in Fig. 10. This means that the coordinate dependence of the nonadiabatic transmission probability on the seam surface is important and should be taken into account as is done explicitly in Eq. (18). 

Yoshizawa, K., Shiota, Y., Yamabe, T., 1999, Intrinsic Reaction Coordinate Analysis of the Conversion of Methane to Methanol by an Iron-Oxo Species A Study of Crossing Seams of Potential Energy Surfaces , J. Chem. Phys., Ill, 538. 

It is unclear exactly how the two potential surfaces, and hence the interaction regions between them, behave as the parent molecules bend. Our experimental results indicate that the more bent the ozone molecules are as they dissociate the more effectively is the available energy channelled into the OA T, ) fragment vibration. It is possible that as the parent molecules bend, the crossing seams move to a region on the repulsive state that more strongly favors the production of vibrationally excited 02(3 ) fragments. 

Recently, a technique (129) for localization of a point on the crossing seam of two energy surfaces has been suggested, followed by a method of going downhill to the minima on both surfaces, which is equivalent to IRC for single PES reactions. 

Spin-coupled calculations revealed crossing seams between potential energy surfaces arising from the I + 02(a) and I + 02 X) asymptotes. In a fully adiabatic treatment of this problem the surface crossings were avoided and somewhat difficult to locate. To facilitate interpretation of the adiabatic results, diabatic calculations were preformed with coupling between states from different asymptotes suppressed. Surface intersections were allowed and readily located using the diabatic treatment. 

Lowest Energy Point on the Crossing Seam Between Two Potential Surfaces Using the Energy Gradient. 

Fig. 2. Perspective view of the crossing seam for the H3 DMBE potential energy surface using the coordinates R2, Rs,a), with the valence angle fixed at a = 60°. Also indicated in dash and dash-dot are the lines corresponding to Q2 = 0 and Q3 = 0, where...

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