def kinetic_energy(be, hv, psi):
    """Calculates the kinetic energy (KE) with a Mg source (Dalhousie default):

    be  : binding energy (BE [eV])
    psi : Work function (Psi [eV])
    hv  : Phonton energy (h*nu [eV])
    """
    return hv - be - psi
