The Characteristic Gibbs Function

The concept of a dielectrochemical potential introduced in the previous section is already implicit in Guggenheim s treatment of dielectrics in the presence of external fields. In order to apply the familiar criteria for reversible (equilibrium) processes and irreversible (nonequilibrium) processes in terms of an appropriate Gibbs function, Guggenheim introduced the characteristic Gibbs function in the presence of electric fields by a transformation. We may express the transformed Gibbs free energy as 

The differential work term of the field-dipole interaction is 

By Mj = N mj co% 5 , Mj refers to the average of the field-parallel contributions of all individual moments m,. 

In this context. Eigen and DeMaeyer used the relationship G = G D E, with D = F-P. where P is the polarization per unit volume and V is the volume. 

It is now useful to denote the chemical potential of the (dipolar) species Bj in the presence of an electric field by a special symbol  

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Substituting Eq. (4.10) into (4.11) finally leads to the characteristic Gibbs function for chemically open systems in electric fields ... 

For isobaric-isothermal conditions the characteristic Gibbs function reduces to... 

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