Efficient Ewald electrostatic calculations for large systems

A method is described which improves the efficiency of Ewald simulations of large condensed phase systems. This is achieved by partitioning the real space sum into a short and long range component. The long range component is calculated every time the pair list is generated and included in subsequent steps using a multiple time step algorithm. The corresponding increase in the effective cutoff distance results in an algorithm which is only slightly more expensive than a traditional cutoff simulation, but with fewer artifacts than obtained using a cutoff. The method is tested on a 1.0 M solution of sodium chloride.