Dear Davide, Mete-GGA functional such as TPSS are known to have convergency problems and numerical instabilities during scf cycles, specifically when the unit-cell contains a lot of free volume, such as in your case probably. You can try to decrease the size of the unit-cell in order to minimize the free space it contains. Of course, this will be at the expense of the inter-polyemer interaction you probably want to avoid.
Nevertheless, this will probably not cure your problem, which to my knowledge has no other solution than changing the meta-GGA functional to a GGA one. Best regards, Yves Le 24 avr. 2014 ? 13:36, Davide Tiana a ?crit : > > 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 > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum
