Long Range Versus Short Range Interactions in Zeolites
Models based on short range and long range (mainly electrostatic) interaction effects in describing the properties of zeolites are critically examined. Starting point is the Hamiltonian operator. Depending on the property under investigation, the (long range) external potential terms will have to be included in the model. Geometries can be predicted adequately by accounting for short range (repulsive and attractive) interactions only. Energy calculations and molecular interactions are much more sensitive to including the external potential in the calculations because of the predominant influence of the Madelung potential on the charge distribution for inorganic systems. For interactions of molecules with the surface, the absolute magnitude is of no importance, but the potential gradient will determine the properties. The cation distribution is adequately described using short-range interactions only, and is seemingly independent of the A1 distribution pattern in the framework. The same could apply to the protons, in which case we might have to revise the current concepts concerning Broensted acidity in zeolites.
KeywordsLong Range Point Charge Range Interaction Hamiltonian Operator Cation Distribution
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