Dear Ayedun, Try using a higher ecutwfc, like 50 for example. Also a smaller degauss value. Finally set the ecutrho to 4*ecutwfc if your pseudopotential is not US, and to 12*ecutwfc if it is.
It`s also a good idea to specify the number of bands, to make sure you got enough ones on the calculation. If unsure you can just use a high value and reduce it after a test calculation to compensate for the extra empty bands. Choose a single ibrav value (if unsure, go for the experimental value or close to it) and play with these parameters, checking how the total energy changes with them. Once you get convergence on the total energy, then you'll have a reliable setup that will allow you to change the ibrav values and obtain good curves. Sincerely, Giovani Faccin UFMS/Brazil 2012/4/8 funmi ayedun <funmiayedun at yahoo.com> > Dear All, > > Good day all, I am a new user in quantum espresso, I am working on anatase > TiO2 (with hexagonal structure) but I have problem with convergence test > for lattice parameter for TiO2 system. I have tried to vary celldm 1 from > 8.2 to 9.0Bohr but I was unable get a convergence result. Also, I tried to > vary celldm 3 from 0.2441 to 1.3441Bohr and keeping celldm 1 constant, I > was unable to get convergence as well. I have my input file below. > > &control > calculation = 'scf', > restart_mode='from_scratch', > prefix='TiO2' > pseudo_dir='/home/funmilayo/espresso-4.2.1/pseudo', > outdir='./', > tprnfor = .true. > tstress = .true. > / > &system > ibrav=6, celldm(1)= 8.6808, celldm(3)= 0.7450, > nat=3, ntyp=2,occupations='smearing', smearing='marzari-vanderbilt', > degauss=0.02 > ecutwfc= 25.0, > / > &electrons > mixing_beta = 0.7 > diagonalization='davidson' > conv_thr = 1.0d-8 > / > ATOMIC_SPECIES > Ti 47.867 Ti.blyp-sp-van_ak.UPF > O 15.994 O.blyp-van_ak.UPF > ATOMIC_POSITIONS > Ti 0.00000000 0.00000000 0.00000000 > O 0.33333333 0.33333333 0.33333333 > O 0.80000000 0.20000000 0.50000000 > K_POINTS (automatic) > 6 6 6 0 0 0 > > Can anyone please tell me where I have gone wrong. > Thank you all. > > > Ayedun Oluwafunmilayo, > PhD student, > Department of Physics, > University of Agriculture, > Abeokuta, > Nigeria. > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120408/dffaf7f0/attachment.htm
