[Pw_forum] hybrid calculation with dexx negative

[mohnish pandey]

Hi Valentina,

May be it will help:
http://qe-forge.org/pipermail/pw_forum/2013-November/102690.html


On Thu, Jan 30, 2014 at 10:52 AM, DELLACA' Valentina (CRF) <
valentina.dellaca at crf.it> wrote:

> Dear all,
>
> We are performing surface calculations with hybrid functional, and for the
> following surface structure at the moment the error saying: 'dexx is
> negative, error # 1 , check that exxdiv_treatment is appropriate for the
> system' is giving us some troubles. We already tried to change the distance
> between surfaces, changing celldm(3), around its optimized value 2.39, we
> changed also mixing_beta to 0.3, and we tried with few different k point
> grids. None of this attempt was successful in solving the error. We also
> changed the occupations to smearing, and we gave a small degauss (1d-20),
> but then (with many celldm(3)) it was not even converging the first scf.
>
> Any suggestion on how to fix this error?
>
> Thank you,
>
> Regards,
>
> Valentina
>
>
>
> &CONTROL
>
>                   calculation = 'scf',
>
>                  restart_mode = 'from_scratch',
>
>                        outdir = '',
>
>                       pseudo_dir  = '',
>
>                       prefix = 'ta2o5' ,
>
>                       disk_io = 'default',
>
> /
>
>   &SYSTEM
>
>                         ibrav = 8,
>
>                     celldm(1) =  14.241893092,
>
>                     celldm(2) =  0.822831603,
>
>                     celldm(3) =  2.39,
>
>                           nat = 38,
>
>                          ntyp = 2,
>
>    ecutwfc=70, nbnd=700, occupations='fixed',
>
>      input_dft = 'PBE0',
>
>     exxdiv_treatment = 'gygi-baldereschi'
>
>     x_gamma_extrapolation=.true.
>
>     nqx1 = 1 , nqx2 = 1, nqx3 = 1
>
> /
>
> &electrons
>
>     conv_thr=1.0d-9, mixing_beta=0.5
>
> /
>
> ATOMIC_SPECIES
>
> Ta   180.95  Ta.pbe-mt-fhi.UPF
>
> O   15.999   O.pbe-mt-fhi.UPF
>
>
>
>
>
>
>
> ATOMIC_POSITIONS (angstrom)
>
> O        0.813278477   4.617988459   8.007774872
>
> O        2.023476210   0.776972843   8.441046448
>
> Ta       1.546871435   2.767467670   7.799599600
>
> O        3.366054079   3.877523758   8.440539307
>
> Ta       3.843027211   5.867856582   7.799473875
>
> O        5.792152399   5.359043398   8.438587876
>
> Ta       5.314346183   3.366897623   7.799507537
>
> O        4.577766398   1.516932685   8.008262086
>
> O        7.134074123   2.258690100   8.438344309
>
> Ta       7.612245398   0.266340494   7.800172819
>
> O        3.496914324   5.857316984   5.883545751
>
> O        5.660946844   3.375012981   5.883534436
>
> O        1.890303432   2.756178342   5.883603671
>
> O        7.271488124   0.274248516   5.883520878
>
> O        5.637305636   5.330921586   3.862497327
>
> O        3.523414777   3.905957403   3.865060769
>
> O        0.813798912   4.618557268   3.867613313
>
> O        1.868771197   0.805909423   3.864412229
>
> O        4.578829938   1.517577526   3.866842485
>
> O        7.290961638   2.230024951   3.864847639
>
> O        3.497903745   5.858106076   1.841803379
>
> O        1.888736406   2.757775274   1.841813170
>
> O        5.659923444   3.372905841   1.841275566
>
> O        7.273010266   0.273369852   1.841504469
>
> O        5.792500075   5.359007930  -0.713580871
>
> O        3.366000630   3.876131545  -0.715282591
>
> O        0.813543928   4.618155682  -0.280250553
>
> O        2.025151305   0.776423231  -0.714789822
>
> O        4.578389288   1.516157053  -0.281620473
>
> O        7.134187444   2.259560146  -0.714019402
>
> Ta       3.631274701   5.991239815   3.862567887
>
> Ta       1.760248756   2.890622602   3.862584360
>
> Ta       5.528096689   3.245167855   3.862383012
>
> Ta       7.400881489   0.144629430   3.862458735
>
> Ta       7.613260471   0.266812681  -0.075602588
>
> Ta       5.314089138   3.366439123  -0.075243654
>
> Ta       3.843827877   5.867144678  -0.074583652
>
> Ta       1.546399836   2.767291744  -0.074953513
>
>
>
>
>
>
>
> K_POINTS {automatic}
>
> 2 2 1  0 0 0
>
>
>
> Valentina Dellacà
> Group Materials Labs
> PA&CT - Virtual Analysis & Materials Modelling
>
>
> Centro Ricerche Fiat S.C.p.A.
> Sede legale e amministrativa: Strada Torino, 50
> 10043 Orbassano (TO), Italia
> Tel  +39 011 9083138
> Fax +39 011 9083666
>
> www.crf.it
>
>
>
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>



-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey,
PhD Student,
Center for Atomic-scale Materials Design,
Department of Physics,
Technical University of Denmark
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