Prototype Molecules in Effective Potentials

In polar systems, including dipolar subunits or ionic constituents quite important electrostatic fields may occur in the volume occupied by the relevant cluster. Various experimental and theoretical estimates suggest that the electrostatic field may attain 10 to 50 V/nm in systems like zeolites [133, 186] or protein active sites [187]. 

The effect of this strongly inhomogeneous external potential has to be included in the quantum chemical calculations, because its influence is probably significant on the charge distribution of the prototype molecule. 

A common procedure is to include the potential of a representative set of partial charges of the environment in the Hamilton operator or the Fockian of the prototype molecule [188, 189]. This means that the core Hamiltonian is modified by a set of nuclear attraction integrals with partial point charges  

This method has been applied, for example, for the modeling of enzymatic reactions including environmental effects [190-193]. 

Quite recently a similar procedure has been applied to hydrogen bonded complexes in zeolites, although the form of the Fock operator is different. The interaction energy 

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