code: def delta_E( reactants, products, check_balance=True ):
      
      if check_balance:
          if delta_stoichiometry( reactants, products ) != {}:
              raise ValueError( "reaction is not balanced: {}".format( delta_stoichiometry( reactants, products) ) )
      return sum( [ r.energy for r in products ] ) - sum( [ r.energy for r in reactants ] )
docs: Calculate the change in energy for reactants --> products.
      
      Args:
          reactants (list(vasppy.Calculation): A list of vasppy.Calculation objects. The initial state.
          products  (list(vasppy.Calculation): A list of vasppy.Calculation objects. The final state.
          check_balance (bool:optional): Check that the reaction stoichiometry is balanced. Default: True.
  
      Returns:
          (float) The change in energy.