Get the normalized correction term Δμ for chemical potential of a gas
        phase consisting of element at given temperature and pressure,
        referenced to that in the standard state (T_std = 298.15 K,
        T_std = 1 bar). The gas phase is limited to be one of O2, N2, Cl2,
        F2, H2. Calculation formula can be found in the documentation of
        Materials Project website.

        Args:
            element (string): The string representing the element.
            temp (float): The temperature of the gas phase.
            pres (float): The pressure of the gas phase.

        Returns:
            The correction of chemical potential in eV/atom of the gas
            phase at given temperature and pressure.

def get_chempot_correction(element, temp, pres):
        """
        Get the normalized correction term Δμ for chemical potential of a gas
        phase consisting of element at given temperature and pressure,
        referenced to that in the standard state (T_std = 298.15 K,
        T_std = 1 bar). The gas phase is limited to be one of O2, N2, Cl2,
        F2, H2. Calculation formula can be found in the documentation of
        Materials Project website.

        Args:
            element (string): The string representing the element.
            temp (float): The temperature of the gas phase.
            pres (float): The pressure of the gas phase.

        Returns:
            The correction of chemical potential in eV/atom of the gas
            phase at given temperature and pressure.
        """
        if element not in ["O", "N", "Cl", "F", "H"]:
            return 0
        std_temp = 298.15
        std_pres = 1E5
        ideal_gas_const = 8.3144598
        # Cp and S at standard state in J/(K.mol). Data from
        # https://janaf.nist.gov/tables/O-029.html
        # https://janaf.nist.gov/tables/N-023.html
        # https://janaf.nist.gov/tables/Cl-073.html
        # https://janaf.nist.gov/tables/F-054.html
        # https://janaf.nist.gov/tables/H-050.html
        Cp_dict = {"O": 29.376,
                   "N": 29.124,
                   "Cl": 33.949,
                   "F": 31.302,
                   "H": 28.836}

        S_dict = {"O": 205.147,
                  "N": 191.609,
                  "Cl": 223.079,
                  "F": 202.789,
                  "H": 130.680}
        Cp_std = Cp_dict[element]
        S_std = S_dict[element]
        PV_correction = ideal_gas_const * temp * np.log(pres / std_pres)
        TS_correction = - Cp_std * (temp * np.log(temp)
                                    - std_temp * np.log(std_temp)) \
                        + Cp_std * (temp - std_temp) \
                                 * (1 + np.log(std_temp)) \
                        - S_std * (temp - std_temp)

        dG = PV_correction + TS_correction
        # Convert to eV/molecule unit.
        dG /= 1000 * InterfacialReactivity.EV_TO_KJ_PER_MOL
        # Normalize by number of atoms in the gas molecule. For elements
        # considered, the gas molecules are all diatomic.
        dG /= 2
        return dG