The proper selection of any characteristic functions [G,F, S, H, U} relies on the experimental conditions. For isothermal transformation under the isobaric condition Global Gibbs Free energy is a good choice. Global Helmholtz free energy should be proper choice for the isothermal isochoric transformations which corresponds to isovolumic reactions in simple case but in general it may be used for the workless walls or boundaries including stored elastic strain energy. Enthalpy and Internal Energy may be selected for the adiabatic (isentropic changes where entropy stays invariant) under the isobaric and isovolumic transformations, respectively.

Under the infinitesimal changes in above conditions ( dT, dP or Dv) Gibbs and Helmholtz free energies, respectively, show minimum and the stable conditions corresponds to reversible isothermal state described by dG=0 and dF=0. Similarly for given infinitesimal changes in S and P or V reversible enthalpy and internal energy variations show minimum and dH=0 and dU=0.

Note: For the natural isothermal processes I have developed a mathematical theory (As a boundary value problem suitable for computer simulations) for the isochoric as well as isobaric processes with applications for several rather complicated systems appeared in the field of Materials Science during the last twenty years. You may find related published papers in TG.

This theory covers the growth part of the phase transition, which may take place simultaneously with the surface morphological evolutions induced by the surface drift diffusion driven by electrostatic and elastostatic forces including the capillarity.

Dear Prof. Tarık Ömer Oğurtanı,

Thank you so much for your time and information. I will search those papers.

Regards

Here is link

https://youtu.be/ZT6Nwf5wdG0

This video shows how to interpret thermodynamic parameters △G°, △H°, and △S° from experimental data. #aminulcheminnovation #AminulSir #aminulchem #DrMdAminulIslam #DMAI #MAI

https://youtu.be/LGuDshiNOmQ