Figure 1.

Schematic illustration of a free energy landscape dominated by a slow process. The timescales associated with a system will often reflect “activated” (energy-climbing) processes, although they could also indicate diffusion times for traversing a rough landscape with many small barriers. In the figure, the largest barrier is associated with the slowest timescale t_slow, and the danger for conventional MD simulations is that the total length of the simulation may be inadequate to generate the barrier crossing.