def no_overlap_dhkl(Lambda, C_3=1):
    """
    Largest d-spacing producing no CBED order overlap if the probe size is diffraction limited.
    Params:
    Lambda: electron wavelength in Å
    C_3: spherical aberration constant in mm, default 1.
    Returns:
    largest d_hkl without CBED order overlap.
    """
    C_3 *= 1.e7
    return 0.7874 * C_3 ** (1. / 4) * Lambda ** (3. / 4)