Long-range forces microscopic approach

The alternative theoretical scheme for studying chemical reactivity in solution, the supermolecule approach, allows for the investigation of the solvation phenomena at a microscopic level. However, it does not enable the characterization of long-range bulk solvent forces moreover, the number of solvent molecules required to properly represent bulk solvation for a given solute can be so large that to perform a quantum chemical calculation in such a system becomes prohibitively expensive. ... 

The most common and possibly most versatile SPM is the atomic force microscope (AFM). The AFM relies on the principle of the atomic forces exerted between two objects as they are brought close to each other (Fig. 2). At a distance of tens to hundreds of angstroms, the interatomic forces are attractive (predominantly due to long-range van der Waals forces). On approaching the surface to a distance of a few angstroms, the force becomes repulsive. To observe this phenomenon. 

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