After a period of simulation, the lid energy is shifted to higher energy to increase the configurational space that is available to the trajectory, allowing transitions to new structures separated by energy barriers lower than the new energy lid. Therefore, when a trajectory visits the energy basin of a new local minimum, the energy barrier between the new and initial minima can be estimated as the current energy lid. An assumption here is that the step size of allowed perturbations is small enough that attempted moves cannot jump through energy barriers. The sampling under each energy lid needs, in principal, to be ergodic, although this is hindered by the required small step size.