Energy long-range interaction

If the simulated system uses periodic boundary conditions, the logical long-range interaction includes a lattice sum over all particles with all their images. Apart from some obvious and resolvable corrections for self-energy and for image interaction between excluded pairs, the question has been raised if one really wishes to enhance the effect of the artificial boundary conditions by including lattice sums. The effect of the periodic conditions should at least be evaluated by simulation with different box sizes or by continuum corrections, if applicable (see below). 

This basic LFER approach has later been extended to the more general concept of fragmentation. Molecules are dissected into substructures and each substructure is seen to contribute a constant inaement to the free-energy based property. The promise of strict linearity does not hold true in most cases, so corrections have to be applied in the majority of methods based on a fragmentation approach. Correction terms are often related to long range interactions such as resonance or steric effects. 

Ion-ion interactions are long-range interactions decreasing only with r 1 and their mean interaction energy 0M is given by3)... 

Simonson, T. Archontis, G. Karplus, M., Continuum treatment of long-range interactions in free energy calculations. Application to protein-ligand binding, J. Phys. Chem. B 1997, 101, 8349-8362... 

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