Area specific resistance ASR for ion transfer across the membrane can be given in terms of fundamental charge transfer mechanisms and may be described by models such as the Butler-Volmer model . For most solid-state membranes, area specific resistance (ASR) of the electronic defects is much greater than the ASR of permittable species. Note that the electron transport through the electrolyte is negligible, however, based on the local equilibrium assumption, electronic transport cannot mathematically be zero. The GHK equation defines the cell potential for multi-species conductors in terms of the individual Nernst voltages and transport parameters.