The Potential of Mean Constraint Force

Having found a more convenient expression to calculate d.4/d what remains to be developed is an algorithm which overcomes the sampling difficulty associated with high energy barriers. There are two approaches to this problem. The first one, called 

The second approach, ABF, consists of estimating the average force at different and removing it from the system. This leads to a diffusive-like motion along and a much better convergence of the calculation. We will describe ABF in Sect. 4.6. 

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The steepest descent (4.48) requires calculation of dA/d . Laio and Parrinello chose to estimate this term by performing short constrained molecular dynamics simulations and computing the potential of mean constraint force (see Carter et al. [45]). 

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