Rare events by constrained molecular dynamics

We present a computationally efficient molecular dynamics method, based on holonomic constraints, devised to estimate the rate constants of rare activated events of short duration. We assume that the process is described by a reaction coordinate ξ(r), a well-defined function in configuration space, and we constrain the system at the `bottleneck' region by prescribing the value of ξ(r). MD trajectories sample phase space according to a biased configurational distribution and averages can be taken from such a new Blue Moon ensemble, with suitable reweighting, to study rare events.