One reason for needing a more global picture of the crystal energy landscape is to distinguish between structures occupying deep and shallow energy minima, ie. are the energy barriers surrounding the structure large or small? An important observation that has been made is that structures corresponding to known polymorphs are often connected to multiple, shallow energy minima by small energy barriers ; traditional CSP methods would suggest each of these minima as possible alternative polymorphs, while a knownledge of small energy barriers separating such structures would show that they can merge into fewer distinct structures due to thermal energy at the temperature of interest. Thus, not distinguishing between deep and shallow energy minima contributes to the over-prediction of polymorphism .