Potential energy as a collective variable

In the last three subsections we saw how carefully designed CV can be used as suitable reaction coordinates. We consider here the possibility of using the potential energy as a CV. 

In a later work, Bonomi et al. showed that it is possible to perform a WTMetaD simulation on the potential energy by sampling the so-called well-tempered ensemble. This ensemble is characterized by a parameter y, which is related to the usual parameter AT by y = In the well-tempered ensemble the distribution of the potential energy is not flat but instead is related to the canonical distribution P U) by oc P(U) /y. The effect 

Interestingly, in a recent paper it has been shown that it is possible to dissect the potential energy and use as a CV only a relevant portion of it, namely, the Debye-Hiickel interaction between two molecules. Although in that paper this CV was biased using steered molecular dynamics, the extension to umbrella sampUng or metadynamics is straightforward. 

---