Complex step-size dependences in tracking a simple two-body dynamics

In molecular simulations, one of the most difficult points is to track the real dynamics of many-body systems from the first principle. The present study shows that step-size dependences have an unexpected effect on simulation results, even when we use the standard high-precision numerical integrators to apply to a simple system with a two-body interaction. The validity of our analysis is checked by the theory of adiabatic approximations.