Combining Rules for Molecular, Particle and Surface Interactions

2 Combining Rules for Molecular, Particle and Surface Interactions 

It is possible to express any molecular interaction semi-quantitatively, independent of the type of interaction involved. All particle-particle, particle-surface, surface-surface and sometimes even complex multi-component interactions obey the combining rules of molecular interactions, except hydrogen-bonding interactions. 

When two molecules are located at a given separation, their molecular interaction is proportional to the product of their most effective molecular property. For example, if molecule (1) has some effective molecular property such as dispersion forces, then we have A, °c a, and similarly A2 tt2 for molecule (2), where A denotes the molecular property and a the polarizability of these molecules. Then the binding potential energy between molecules (1) and (2) in contact maybe expressed as 

The change in the interaction potential energy, AV, on going from the dispersed to associated state can be calculated as 

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In Section 7.2 we described combining rules for molecular, particle and surface interactions in a two-component system of (1) and (2). In this section, we will examine the combining rules when the molecules, particles or surfaces of (1) and (2) are placed in a solvent medium (3). 

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