Method and system for calculating the electrostatic force due to a system of charged bodies in molecular modeling

In the molecular modeling of a molecular system represented by constituent charged rigid bodies, the electrostatic interactions are computed between the rigid bodies, rather than the individual atoms which constitute the bodies. Multipole representations of the charge distribution of the bodies are used, and the total translational force and moment acting on each rigid body are computed using approximations of the form: 1 F ~ 2 , M ~ 2 = u 3 x 1 q 2 + M 3 x 3 p 2 + N 3 x 5 Q ^ 2 + T 3 x 10 O ^ 2 . When the approximations are applied to small or medium-sized molecules, such as biomolecules of current interest such as proteins, the electrostatic force computations according to the approximations of the present invention are faster than the direct or fast multipole methods.