integer :: optics_nbands

The number of bands at each k-point when performing an optical spectrum calculation.

If OPTICS_NBANDS is present in the parameter file, the value of bs_nbands is determined by this keyword.

If OPTICS_NEXTRA_BANDS is specified ${\tt optics\_nbands} = {\tt max(nup,ndown)} + \\ {\rm OPTICS\_NEXTRA\_BANDS}$.

If OPTICS_PERC_EXTRA_BANDS is specified ${\tt optics\_nbands} = {\tt max(nup,ndown)} \times ( 1 + \frac{\rm OPTICS\_PERC\_EXTRA\_BANDS}{100})$.

The default value of this parameter is .