def _Melting_Pressure(T, ice="Ih"):
    """Melting Pressure correlation

    Parameters
    ----------
    T : float
        Temperature, [K]
    ice: string
        Type of ice: Ih, III, V, VI, VII.
        Below 273.15 is a mandatory input, the ice Ih is the default value.
        Above 273.15, the ice type is unnecesary.

    Returns
    -------
    P : float
        Pressure at sublimation line, [MPa]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 251.165 ≤ T ≤ 715

    Examples
    --------
    >>> _Melting_Pressure(260)
    8.947352740189152e-06
    >>> _Melting_Pressure(254, "III")
    268.6846466336108

    References
    ----------
    IAPWS, Revised Release on the Pressure along the Melting and Sublimation
    Curves of Ordinary Water Substance, http://iapws.org/relguide/MeltSub.html.
    """
    if ice == "Ih" and 251.165 <= T <= 273.16:
        # Ice Ih
        Tref = Tt
        Pref = Pt
        Tita = T/Tref
        a = [0.119539337e7, 0.808183159e5, 0.33382686e4]
        expo = [3., 0.2575e2, 0.10375e3]
        suma = 1
        for ai, expi in zip(a, expo):
            suma += ai*(1-Tita**expi)
        P = suma*Pref
    elif ice == "III" and 251.165 < T <= 256.164:
        # Ice III
        Tref = 251.165
        Pref = 208.566
        Tita = T/Tref
        P = Pref*(1-0.299948*(1-Tita**60.))
    elif (ice == "V" and 256.164 < T <= 273.15) or 273.15 < T <= 273.31:
        # Ice V
        Tref = 256.164
        Pref = 350.100
        Tita = T/Tref
        P = Pref*(1-1.18721*(1-Tita**8.))
    elif 273.31 < T <= 355:
        # Ice VI
        Tref = 273.31
        Pref = 632.400
        Tita = T/Tref
        P = Pref*(1-1.07476*(1-Tita**4.6))
    elif 355. < T <= 715:
        # Ice VII
        Tref = 355
        Pref = 2216.000
        Tita = T/Tref
        P = Pref*exp(1.73683*(1-1./Tita)-0.544606e-1*(1-Tita**5) +
                     0.806106e-7*(1-Tita**22))
    else:
        raise NotImplementedError("Incoming out of bound")
    return P
Melting Pressure correlation

    Parameters
    ----------
    T : float
        Temperature, [K]
    ice: string
        Type of ice: Ih, III, V, VI, VII.
        Below 273.15 is a mandatory input, the ice Ih is the default value.
        Above 273.15, the ice type is unnecesary.

    Returns
    -------
    P : float
        Pressure at sublimation line, [MPa]

    Notes
    ------
    Raise :class:`NotImplementedError` if input isn't in limit:

        * 251.165 ≤ T ≤ 715

    Examples
    --------
    >>> _Melting_Pressure(260)
    8.947352740189152e-06
    >>> _Melting_Pressure(254, "III")
    268.6846466336108

    References
    ----------
    IAPWS, Revised Release on the Pressure along the Melting and Sublimation
    Curves of Ordinary Water Substance, http://iapws.org/relguide/MeltSub.html.