text: import autograd.numpy as np
  
  
  def graphite_mcmb2528_ocp_Dualfoil1998(sto):
      """
         Graphite MCMB 2528 Open Circuit Potential (OCP) as a function of the
         stochiometry. The fit is taken from Dualfoil [1]. Dualfoil states that the data
         was measured by Chris Bogatu at Telcordia and PolyStor materials, 2000. However,
         we could not find any other records of this measurment.
  
         References
         ----------
         .. [1] http://www.cchem.berkeley.edu/jsngrp/fortran.html
         """
  
      u_eq = (
          0.194
          + 1.5 * np.exp(-120.0 * sto)
          + 0.0351 * np.tanh((sto - 0.286) / 0.083)
          - 0.0045 * np.tanh((sto - 0.849) / 0.119)
          - 0.035 * np.tanh((sto - 0.9233) / 0.05)
          - 0.0147 * np.tanh((sto - 0.5) / 0.034)
          - 0.102 * np.tanh((sto - 0.194) / 0.142)
          - 0.022 * np.tanh((sto - 0.9) / 0.0164)
          - 0.011 * np.tanh((sto - 0.124) / 0.0226)
          + 0.0155 * np.tanh((sto - 0.105) / 0.029)
      )
  
      return u_eq
  