Asymmetric interaction parameters, interface

Thus, the first term includes dispersion, polar and induction effects, while the latter includes asymmetric interactions, e.g. hydrogen bonding. Equation (6.3.1) is valid for both solid and liquid interfaces. Three liquids and contact angle data must be used for determining the three parameters of a solid smface, and thus... 

Because the electron donating and the electron accepting sites at a surface or interface are different and play different roles in the interfacial interactions, the polar properties of a surface are inherently asymmetrical and must he described by two parameters. This is very different from the LW interactions where, for example, (Eq. 5.33) ... 

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