code: def Cvgm(self):
          r'''Gas-phase ideal-gas contant-volume heat capacity of the chemical at
          its current temperature, in units of [J/mol/K]. Subtracts R from
          the ideal-gas heat capacity; does not include pressure-compensation
          from an equation of state.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cvgm
          27.13366316134193
          '''
          Cpgm = self.HeatCapacityGas(self.T)
          if Cpgm:
              return Cpgm - R
          return Nonf Cvgm(self):
          r'''Gas-phase ideal-gas contant-volume heat capacity of the chemical at
          its current temperature, in units of [J/mol/K]. Subtracts R from
          the ideal-gas heat capacity; does not include pressure-compensation
          from an equation of state.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cvgm
          27.13366316134193
          '''
          Cpgm = self.HeatCapacityGas(self.T)
          if Cpgm:
              return Cpgm - R
          return None
docs: r'''Gas-phase ideal-gas contant-volume heat capacity of the chemical at
          its current temperature, in units of [J/mol/K]. Subtracts R from
          the ideal-gas heat capacity; does not include pressure-compensation
          from an equation of state.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cvgm
          27.13366316134193