Distinguished reaction coordinate DRC

We often define a reaction path in the following way. First, we make 

In 49 B.C. Julius Caesar with his Roman legions crossed the Rubicon river (the border of his province of Gaul), and this initiated a civil war with the central power in Rome. His words, aka iacta esf (the die is cast) became a symbol of a final and irreversible decision. 

As a matter of fact, the formation of van der Waals complexes may also belong to this group. However in large systems, when precise docking of molecules take place, the final docking may occur with a steric barrier. 

A deficiency of the DRC is an arbitrary choice of the distance. The energy profile obtained (the potential energy vs s) depends on the choice. Often the DRC is reasonably close to the reactant geometry and becomes misleading when close to the product value (or vice versa). There is no guarantee that such a reaction path passes through the saddle point. On top of this other coordinates may undergo discontinuities, which feels a little catastrophic. 

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Potential Energy Minima and Saddle Points Distinguished Reaction Coordinate (DRC)... 

DRC Distinguished Reaction Coordinate A selected distance ehanging from the... 

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