code: def Eandg(rOH, thetaHOH):
      """ "
      Arguments: (internal coordinates of the water molecule)
  
      rOH            O-H bond distance
      thetaHOH       H-O-H bond angle
  
  
      Returns:
  
      E              Molecular force field energy
      grOH           O-H bond stretch gradient
      grthetaHOH     H-O-H bond angle bend gradient
  
  
      Force field parameters:
  
      kOH            Harmonic force constant, O-H bond strech
      rOHe           Equilibrium distance, O-H
      kHOH           Harmonic angle bend force constant, H-O-H angle bend
      thetaHOHe      Equilibrium angle, H-O-H
  
      """
  
      kOH = 50.0
      rOHe = 0.95
      kHOH = 50.0
      thetaHOHe = 104.5
  
      E = (
          2 * kOH * (rOH - rOHe) ** 2
          + kHOH * (thetaHOH - thetaHOHe) ** 2
      )
      grOH = 2 * kOH * (rOH - rOHe)
      grthetaHOH = 2 * kHOH * (thetaHOH - thetaHOHe)
  
      return (E, grOH, grthetaHOH)
  
label_desc: Use image node_id 1 for calling a global function with example usage: Eandg(rOH, thetaHOH) and returns: E,  grOH,  grthetaHOH