Presently simulations of bimolecular systems include a very large numbers of atoms ten to hundred of thousands atoms. They are involved over timescales of many nanoseconds. The accurate computation of electrostatic and van der Waals interactions is the most difficult task in computer modeling. The most time consuming part of any molecular dynamics simulation is the calculation of the electrostatic interactions. There interactions fall off as 1/r, where r is the reparation between charges, and have consequently to be considered as long-range.