Calculate seebeck effective mass at a certain carrier concentration
        eta in kB*T units, n in cm-3, T in K, returns mass in m0 units

def seebeck_eff_mass_from_carr(eta, n, T, Lambda):
    """
        Calculate seebeck effective mass at a certain carrier concentration
        eta in kB*T units, n in cm-3, T in K, returns mass in m0 units
    """
    from fdint import fdk

    return (2 * np.pi**2 * abs(n) * 10 ** 6 / (fdk(0.5,eta))) ** (2. / 3)\
            / (2 * constants.m_e * constants.k * T / (constants.h/2/np.pi) ** 2)