def band_extrema_correction(host_cell, host_cell_b):
    """ Compute the correction of the band extrema computed with a functional (Host_Cell)
    in order to retrieve the same gap computed with another functional (Host_Cell_B)
    :param host_cell: Cell object of the host cell calculation
    :param host_cell_b: Cell object of the host cell calculation (with a different functional) """

    de_vbm = host_cell_b.vbm_energy - host_cell.vbm_energy
    de_cbm = host_cell_b.cbm_energy - host_cell.cbm_energy

    return de_vbm, de_cbm