def c_overturned(step):
rbot, rtop = misc.get_rbounds(step)<EOL>cinit, rad = init_c_overturn(step)<EOL>radf = (rtop**<NUM_LIT:3> + rbot**<NUM_LIT:3> - rad**<NUM_LIT:3>)**(<NUM_LIT:1> / <NUM_LIT:3>)<EOL>return cinit, radf<EOL>
Theoretical overturned concentration.

    This compute the resulting composition profile if fractional
    crystallization of a SMO is assumed and then a purely radial
    overturn happens.

    Args:
        step (:class:`~stagpy.stagyydata._Step`): a step of a StagyyData
            instance.
    Returns:
        tuple of :class:`numpy.array`: the composition and the radial position
        at which it is evaluated.