Classical Molecular Dynamics Simulation with the Velocity Verlet Algorithm at Strong External Magnetic Fields

Abstract

We present a new method for incorporating arbitrarily strong static homogeneous external magnetic fields into molecular dynamics computer simulations. Conventional techniques dealing with magnetic fields demand the simulation time step Δ t to be small compared to the Larmor oscillation time 2π/Ω. In our method, in contrast, the magnetic field is built into the propagation equations in such a way as to make the choice of Δ t entirely independent of 2π/Ω. Thus, the time step is determined only by the internal physical properties of the system under consideration. This property of our method is essential for simulating strongly magnetized systems of charged particles in an efficient way. The method is developed in the framework of the second-order Velocity Verlet propagation scheme. However, the underlying concept is independent of this choice, and a generalization to arbitrary order without any reference to a specific propagation scheme is also given.