[Wien] band gap problem for optic calculation

[Tomohiko Tasaka]

Hi,

I try to calculate optical properties for wide-gap insulators.
then, I found that the value of refractive index got worse when band
gap are corrected by GGA+U method or mBJ potential(i.e. underestimate).
so, is this normal behavior? or, am I wrong??

sorry for the vague question, but any information would be appreciated.

Thanks in advance, with best regards,
Tomo