  We present a new approach to efficiently simulate electrolytes confined
between infinite charged walls using a 3d Ewald summation method. The optimal
performance is achieved by separating the electrostatic potential produced by
the charged walls from the electrostatic potential of electrolyte. The electric
field produced by 3d periodic images of the plates is constant, with the field
produced by the transverse images of the charged plates canceling out. We show
that under suitable renormalization, the non-neutral electrolyte confined
between charged plates can be simulated using 3d Ewald summation with a
correction that accounts for the conditional convergence of the resulting
lattice sum. The new algorithm is at least an order of magnitude more rapid
than the usual simulation methods for the slab geometry and can be further sped
up by adopting Particle-Particle Particle-Mesh (P 3 M ) approach.
