Energetic corrugation is the name we have coined to describe a potential energy surface in which only the magnitude (i.e. the energy) of the barrier changes with the location on the surface.

So at a bridge site, for example, the barrier might be 0.5 eV, while at an atop site it might be 0.9 eV, but at both sites the barrier occurs at the same point on the reaction path. This is illustrated here for a simple corrugated Gaussian.

Actually, it can be a bit more subtle than that. For instance, if we considered the elbow PES shown in the previous page, we could change the effective barrier by changing how open the elbow is, while keeping the magnitude of the barrier on the elbow and its position on the reaction path fixed. You can see how this less obvious sort of behaviour works out for the H₂ /Cu(111) PES (but read the geometric and balanced corrugation pages first).

More to come ...