[Pw_forum] tpss: too many bands are not converged

[Davide Tiana]

Dear all,
I've been trying to calculate a polymer using tpss. I already fully  
optimised it with different functional (pbesol, pw91, hse) and  
pseudopotential (nc, paw). For some reason (apologise my ignorance if  
it should be well known) when I try to calculate using tpss nc the  
system simply does not converge crashing with this error:

      Error in routine c_bands (1):
      too many bands are not converged

After some reaserch in old pw-forum mails, I tried decreasing  
mixing_beta=0.2, increasing mixing_ndim=12, as well as mixing mode TF  
and local-TF.
everythings failed.

Does anyone have any tips or idea of why the system can't converge?

Thanks a lot,
Davide