for atom in self.system.atoms:
    verlet = VelocityVerlet(atom)
    force = calc_force(self, atom)
    new_coords = verlet.get_coords(i, force)
    self.tc.add_event([i, atom.move, [new_coords], {}])
    new_force = calc_force(self, atom)
    new_vel = verlet.get_vel(i, force, new_force)
    self.tc.add_event([i, atom.set_vel, [new_vel], {}])