Dynamics on a Potential Energy Surface

Reality suggests that a quantum dynamics rather than classical dynamics computation on the surface would be desirable, but much of chemistry is expected to be explainable with classical mechanics only, having derived a potential energy surface with quantum mechanics. This is because we are now only interested in the motion of atoms rather than electrons. Since atoms are much heavier than electrons it is possible to treat their motion classically. Quantum scattering approaches for small systems are available now, but most chemical phenomena is still treated by a classical approach. A chemical reaction or interaction is a classical trajectory on a potential surface. Such treatments leave out phenomena such as tunneling but are still the state of the art in much of computational chemistry. 

Classical mechanics in volves studying motion (trajectories) on the potential surface where the classical kinetic energy equates to the temperature. The relationship is that the average kinetic energy of 

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Central to the modern approach to chemical reactivity as dynamics on a potential energy surface, is the Born-Oppenheimer approximation.9... 

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