Equilibrium electrode potential under conditions of unit concentration of species involved in the electrode reaction. \[E_{\rm{eq}} = E^{\circ\prime} - (RT/zF)\mathop \sum \limits_i \nu _i \ln(c_i/c^\circ)\] where \(E_{\rm{eq}}\) is the equilibrium electrode potential, \(R\) the gas constant, \(T\) the thermodynamic temperature, \(F\) the Faraday constant, \(z\) the electron number of an electrochemical reaction, \(\nu_{\rm{i}}\) the stoichiometric coefficients (numbers of species) in the equation of the electrode reaction (positive for products and negative for reactants), and \(c_{\rm{i}}\) are the amount concentrations of the species involved (most usually ions).