Before revision:  Exponential time integration schemes remove this stability restriction and allow larger time steps. New multistep exponential propagation iterative methods of orders 4, 5 and 6 are introduced.
After revision:  Exponential integration is employed to enable integrations with significantly larger time step sizes and improve the efficiency of the overall time integration. New multistep-type exponential propagation iterative methods of orders 4, 5 and 6 are introduced.