Electrostatics, different formulations problem

In the 2-level limit a perturbative approach has been used in two famous problems the Marcus model in chemistry and the small polaron model in physics. Both models describe hopping of an electron that drags the polarization cloud that it is formed because of its electrostatic coupling to the enviromnent. This enviromnent is the solvent in the Marcus model and the crystal vibrations (phonons) in the small polaron problem. The details of the coupling and of the polarization are different in these problems, but the Hamiltonian formulation is very similar. ... 

SCMs have many similarities with the way problems for soluble complex equilibria are formulated. For example, the reactions that describe the formation of surface species are described by mass action equations coupled with mass balance constraint. However, the major differences arise from the fact that the complexant ligands are electrically charged and this requires the introduction of an electrostatic component into the mass action equations. In addition, an electrical balance constraint equation is needed to solve the equations. 

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