Potential energy, writing convention

We now return to the definition of the surface excess chemical potential fta given by Equation (2.19) where the partial differentiation of the surface excess Helmholtz energy, Fa, with respect to the surface excess amount, rf, is carried out so that the variables T and A remain constant. This partial derivative is generally referred to as a differential quantity (Hill, 1949 Everett, 1950). Also, for any surface excess thermodynamic quantity Xa, there is a corresponding differential surface excess quantity xa. (According to the mathematical convention, the upper point is used to indicate that we are taking the derivative.) So we may write ... 

In the present problem, write down the function g(r) for a crystalline solid (say, an fee crystal) and show that the expression for the total energy given above reduces to the the conventional pair potential expression. 

Thus, the standard Gibbs energy of solvation A G°p is equal to the solvation Gibbs energy. It is also determined experimentally in the same way as in (7.31). To see that, we write the chemical potential of s in the two phases in the traditional convention, valid only in the limit of ideal gas and ideal dilute solutions ... 

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