Constant-force SMD (CF-SMD) simulation is a considerably straightforward implementation of SMD, in which a constant force is applied to the target groups (e.g., the centerof-mass points) of a system. The force does not depend on the time. Let us now examine how force acts in a molecular system. A one-dimensional reaction coordinate, along which a molecule dissociates, was supposed. The constant force reduces the activation barrier and enhances the unbinding of the molecule (Figure ). The effects of constant forces on the energy landscape have been considerably discussed more than two decades ago . However, no further study has been dedicated to CF-SMD, and it has become oblivious to the computational chemistry community, except for a coarse-grained MD study of protein folding 26 , to our knowledge. This may be because CF-SMD is not straightforward compared to AFM, where constant-velocity pulling (not constant force) is typically used 27 . To extract the kinetics of dissociation under constant forces, models based on Kramers' theory have been devised. Bell's model and the Dudko-Hummer-Szabo (DHS) model provide the dissociation time by fitting the AFM data. Although such models have been utilized in AFM studies, they have rarely been used to analyze MD data.