Now consider the main result, STMD. It is based on the observation that in a standard MD simulation at temperature T 0 with forces derived from the potential energy E ( [ x ] ) , where [ x ] denotes all the positions, the sampling weight for a configuration is e − − E ( [ x ] ) / T 0 . Furthermore, if the forces are derived from a function W ( E ) , the sampling weight is e − − W ( E ( [ x ] ) ) / T 0 .