Dear Matteo Did you also try to play a bit with different exxdiv_treatment methods (with different ecutvcut cutoffs) and/or different PPs? Ciao Giuseppe
Quoting Matteo Gerosa <mgerosa88 at gmail.com>: > Dear Giuseppe, > > thanks for your answer. I'm using the 5.0.2 version of QE plus 5.0.3 > patches. I'm running bulk calculations on MgO (rocksalt structure). The > problem arises only for some q-grids (in one case, also when setting the > q-grid equal to the k-grid), but I haven't understood why. And, as I said > before, shifting the k-grid alone solves the problem. I attach here a > sample input file. > > &CONTROL > calculation = 'scf' , > restart_mode = 'from_scratch' , > outdir = '/home/matteo/qe/tmp/' , > pseudo_dir = '/home/matteo/qe/espresso-5.0.2/pseudo/' , > prefix = 'mgo_hse06' , > verbosity = 'default' , > tstress = .true. , > tprnfor = .true. , > / > &SYSTEM > ibrav = 2, > celldm(1) = 7.9594, > nat = 2, > ntyp = 2, > ecutwfc = 100.0 , > nbnd = 8 , > input_dft = 'hse', nqx1 = 2, nqx2 = 2, nqx3 = 2, > x_gamma_extrapolation = .true., > exxdiv_treatment = 'gygi-baldereschi', > / > &ELECTRONS > conv_thr = 1.0d-9 , > mixing_beta = 0.7 , > / > &IONS > ion_dynamics = 'bfgs' , > / > ATOMIC_SPECIES > Mg 24.30500 Mg.pbe-hgh.UPF > O 15.99940 O.pbe-mt.UPF > ATOMIC_POSITIONS alat > Mg 0 0 0 > O 0.5 0.5 0.5 > K_POINTS automatic > 4 4 4 0 0 0 > > > Thank you for your help. > > Matteo > > > > 2013/11/29 Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it> > >> >> Dear Matteo >> Which QE version are you using? >> I've clashed against similar issues, introduced in the late svn >> versions and (probably) corrected in the latest version, which were >> not present in the stable 5.0.2 version. If you are using the stable >> version, the problem should come out only in the case of strongly >> anisotropic (e.g., surface slabs with large vacuum) cells. Do you find >> it in bulk simulations (ZnO and TiO2, I suppose...:-))?. I've >> performed EXX simulations of these two guys, in the case of bulk as >> well as of surface cells. I did not fall into your dexx errors. >> HTH >> >> Giuseppe >> >> Giuseppe Mattioli >> ISM-CNR >> Italy >> >> Quoting Matteo Gerosa <mgerosa88 at gmail.com>: >> >> > Dear all, >> > >> > I've been trying to calculate band gaps for some semiconductor oxides >> > using hybrid functionals (pbe0, hse, b3lyp). >> > I've learned the choice of the q-grid for computing the exchange energy >> > can be critical. Indeed in some cases I cannot achieve self-consistency >> > and an error message appears in the output file warning that the dexx >> > correction term becomes negative. >> > I guess this is related to the small-q divergence issue for some >> > particular q-grid patterns. In fact, if the k-grid is shifted away from >> > gamma (keeping the q-grid fixed) convergence is achieved. Unfortunately, >> > this doesn't allow me to compute the gap at the gamma point, which I'm >> > interested in. On the other hand, I also obtain convergence if I set >> > "x_gamma_extrapolation=.false.", but this induces large errors for a >> > small number of points in the q-grid. >> > How is it possible to solve the problem and, more importantly, predict >> > in which configurations of the q-grid could the problem arise? Is there >> > any way to shift the q-grid away from gamma? >> > >> > Thanks for any help you can provide. >> > >> > Best regards, >> > >> > Matteo Gerosa >> > >> > -- >> > Matteo Gerosa >> > NanoLab - Micro and Nanostructured Materials Lab >> > Department of Energy, Politecnico di Milano >> > Via Ponzio 34/3 I-20133 Milano, Italy >> > >> > tel. +39 02 2399 6364 >> > web: www.nanolab.polimi.it >> > >> > >> > _______________________________________________ >> > Pw_forum mailing list >> > Pw_forum at pwscf.org >> > http://pwscf.org/mailman/listinfo/pw_forum >> >> >> -- >> ******************************************************** >> - Article premier - Les hommes naissent et demeurent >> libres et ?gaux en droits. Les distinctions sociales >> ne peuvent ?tre fond?es que sur l'utilit? commune >> - Article 2 - Le but de toute association politique >> est la conservation des droits naturels et >> imprescriptibles de l'homme. Ces droits sont la libert?, >> la propri?t?, la s?ret? et la r?sistance ? l'oppression. >> ******************************************************** >> >> Giuseppe Mattioli >> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA >> v. Salaria Km 29,300 - C.P. 10 >> I 00015 - Monterotondo Stazione (RM) >> Tel + 39 06 90672836 - Fax +39 06 90672316 >> E-mail: <giuseppe.mattioli at ism.cnr.it> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://pwscf.org/mailman/listinfo/pw_forum -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.mattioli at ism.cnr.it>
