We just published a novel technique that can be used to enhance sampling in systems where designing effective collective variables is difficult. Our procedure is based on well-tempered metadynamics, and takes advantage of the so called “bias factor” to build a ladder of replicas. In practice, higher replicas are keeping the collective variables at higher temperature. To allow a large number of collective variables to be simultaneously accelerated, we used multiple concurrent metadynamics.
The method is described in details in this paper, just accepted on Journal of Chemical Theory and Computation and is available in PLUMED out of the box. A preprint is available at arXiv:1502.02115.