aV4 max(cV4/1[mol/l],eps) VO(2+) activity aV5 max(cV5/1[mol/l],eps) VO2(+) activity aH max(cH_pos/1[mol/l],eps) H(+) activity aHSO4 max(cHSO4_pos/1[mol/l],eps) HSO4(-) activity aSO4 max(cSO4_pos/1[mol/l],eps) SO4(2-) activity Eeq_pos Nernst(E0_pos,T,aV5*aH^2/aV4) Equilibrium potential i0_pos F_const*k_pos*aV4^(1-alpha_pos)*aV5^alpha_pos*1[mol/l] Exchange current density rd kd*((aH-aHSO4)/(aH+aHSO4)-beta) dissociation rate phil phil_pos Electrolyte potential (for postprocessing) phis phis_pos Electrode potential (for postprocessing)