[Pw_forum] Convergence problem with Pb180Se180 Cluster optimization

Fri Apr 21 18:39:16 CEST 2017

Dear *Prof.  Paolo, *Giuseppe*, *ashkan Thank you for your valuable
suggestions.

After analyzing  the structure I think the whole mess is done  by surface
dangling bonds.Here I don't want to saturate the surface as I have
interested to simulate the excitonic and optical properties of the bear
clusters.

Best regards,

Naren

*Dr. Narendra Nath Ghosh*

*Research Associate*

*University of Gour Banga*

*Department of Chemistry*

*Malda-732102*

*India*

*Phone: +919126667601*

On Fri, Apr 21, 2017 at 9:45 AM, Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> > Use more intense kpoint mesh.
>
> No, this is useless. 0D systems have molecular-like flat rather than
> dispersed energy levels in the reciprocal space. There is no reason to
> sample the
> Brillouin zone with more k-points.
>
> HTH
> Giuseppe
>
> On Friday, April 21, 2017 05:06:42 PM ashkan shekaari wrote:
> > Dear Naren,
> > Increase ecut. Use more intense kpoint mesh.
> >
> > On Apr 21, 2017 4:50 PM, "Giuseppe Mattioli" <
> giuseppe.mattioli at ism.cnr.it>
> >
> > wrote:
> > > Dear Naren
> > > Your calculation is very expensive, and calculations of 0D objects in a
> > > plane-wave/PBC framework are often prone to convergence issues. This
> said,
> > > you
> > > can try to
> > >
> > > 1) perform a simple calculation of the PbSe unit cell with the same
> > > pseudopotentials. Are there similar convergence problems? You are
> using hgh
> > > that
> > > are norm-conserving pseudopotentials (NCPP) and they could require a
> > > richer pw basis set. I would not be surprised if, after proper
> convergence
> > > tests
> > > performed on the unit cell, you ended up with ecutwfc=70~80 Ry. There
> is
> > > no need to specify ecutrho, anyway. It is fixed to a default ecutwfc*4
> value
> > > in the case of NCPP.
> > >
> > > 2) lower mixing_beta, even down to very small values such as 0.05~0.01.
> > > Sometimes it helps to reach convergence (slowly but steady).
> > >
> > > It is impossible to say more without looking at you cluster, but if it
> is
> > > simply cut out from the bulk along low-index directions (e.g., a cube)
> you
> > > have to deal with a mess of surface dangling bonds that want to play
> nasty
> > > charge displacements between occupied and unoccupied electronic levels,
> > > even inducing a metallic character in your cluster. People used to
> > > saturate such dangling bonds with pseudo-H atoms (H atoms having formal
> > > charge
> > > lower or higher than 1.0, depending on the formal valence of the
> saturated
> > > atom). If you don't want to saturate the surface you must keep into
> account
> > > the possibility that the cluster surface reconstruct, and you should
> > > anticipate reconstruction trends by lplacing the atoms nearer to the
> > > expected
> > > final positions. It could be a very difficult task, look at the
> > > instructive story of the Si 7x7 reconstruction in this movie!
> > >
> > > https://www.youtube.com/watch?v=BXdC0NhAMBY
> > >
> > > HTH
> > > Giuseppe
> > >
> > > On Friday, April 21, 2017 04:06:06 AM Narendranath Ghosh wrote:
> > > > Dear all!
> > > >
> > > >
> > > >
> > > > I am currently trying to optimizing a Pb180Se180 cluster using  QE.
> > > >
> > > > But after 83 iterations it didnÃ¢â‚¬â„¢t get converged.
> > > >
> > > > *Input  *
> > > >
> > > > calculation='relax',
> > > >
> > > >   outdir='/staging/op/NAREN_USC/PbSe_360_FINAL_based_Pb68Se68/
> OUTPUT',
> > > >
> > > >   prefix='PbSe-360',
> > > >
> > > >   pseudo_dir='/staging/op/NAREN_USC/PbSe_360_FINAL_based_
> > >
> > > Pb68Se68/pseudo',
> > >
> > > >   verbosity='low',
> > > >
> > > > /
> > > >
> > > >
> > > >
> > > > &SYSTEM
> > > >
> > > >   ibrav=0,
> > > >
> > > >   celldm(1)=90.7068539791d0,
> > > >
> > > >   nat=360,
> > > >
> > > >   ntyp=2,
> > > >
> > > >   ecutwfc=30.0d0,
> > > >
> > > >   ecutrho=120.0d0,
> > > >
> > > >   input_dft='PBE',
> > > >
> > > >   occupations='smearing',
> > > >
> > > >   smearing='gaussian',
> > > >
> > > >   degauss=0.002000d0,
> > > >
> > > > /
> > > >
> > > > &ELECTRONS
> > > >
> > > >   diagonalization='david',
> > > >
> > > >   mixing_mode='plain',
> > > >
> > > >   mixing_beta=0.700d0,
> > > >
> > > > /
> > > >
> > > > &IONS
> > > >
> > > > /
> > > >
> > > > ATOMIC_SPECIES
> > > >
> > > >  Pb 207.200000d0 Pb.pbe-hgh.UPF
> > > >
> > > >  Se 78.960000d0  Se.pbe-hgh.UPF
> > > >
> > > > ATOMIC_POSITIONS {alat}
> > > >
> > > >   Pb   0.4831100000d0   0.4740500000d0   0.4999300000d0
> > > >
> > > >   Se   0.5190800000d0   0.5278700000d0   0.5981100000d0
> > > >
> > > >   Se   0.5901900000d0   0.4712600000d0   0.2154800000d0
> > > >
> > > > Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚
> ¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦
> Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦
> > >
> > > Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦Ã¢â‚¬Â¦.
> > >
> > > > K_POINTS {gamma}
> > > >
> > > >
> > > >
> > > > CELL_PARAMETERS {alat}
> > > >
> > > >   1.000000000000d0  0.000000000000d0  0.000000000000d0
> > > >
> > > >   0.000000000000d0  1.000000000000d0  0.000000000000d0
> > > >
> > > >   0.000000000000d0  0.000000000000d0  1.000000000000d0
> > > >
> > > > *Output*
> > > >
> > > >     iteration # 81     ecut=    30.00 Ry     beta=0.70
> > > >
> > > >      Davidson diagonalization with overlap
> > > >
> > > >      WARNING:     9 eigenvalues not converged in regterg
> > > >
> > > >      ethr =  4.62E-04,  avg # of iterations = 21.0
> > > >
> > > >
> > > >
> > > >      total cpu time spent up to now is    92680.3 secs
> > > >
> > > >
> > > >
> > > >      total energy              =    2098.58547221 Ry
> > > >
> > > >      Harris-Foulkes estimate   =  -16225.87153481 Ry
> > > >
> > > >      estimated scf accuracy    <  209398.02191142 Ry
> > > >
> > > >
> > > >
> > > >      iteration # 82     ecut=    30.00 Ry     beta=0.70
> > > >
> > > >      Davidson diagonalization with overlap
> > > >
> > > >      WARNING:     5 eigenvalues not converged in regterg
> > > >
> > > >      c_bands:  5 eigenvalues not converged
> > > >
> > > >      ethr =  4.62E-04,  avg # of iterations = 20.0
> > > >
> > > >
> > > >
> > > >      total cpu time spent up to now is    95793.4 secs
> > > >
> > > >
> > > >
> > > >      total energy              =    1914.32044477 Ry
> > > >
> > > >      Harris-Foulkes estimate   =  -18801.41916562 Ry
> > > >
> > > >      estimated scf accuracy    <  243341.55571758 Ry
> > > >
> > > >
> > > >
> > > >      iteration # 83     ecut=    30.00 Ry     beta=0.70
> > > >
> > > >      Davidson diagonalization with overlap
> > > >
> > > >      WARNING:   138 eigenvalues not converged in regterg
> > > >
> > > >      ethr =  4.62E-04,  avg # of iterations = 27.0
> > > >
> > > >
> > > >
> > > >      total cpu time spent up to now is    99442.6 secs
> > > >
> > > >
> > > >
> > > >      total energy              =    1659.36438352 Ry
> > > >
> > > >      Harris-Foulkes estimate   =  -15989.48139862 Ry
> > > >
> > > >      estimated scf accuracy    <  138246.99363207 Ry
> > > >
> > > > Any comment to help me getting started is very much appreciated!
> > > >
> > > >
> > > >
> > > > Best regards,
> > > >
> > > > Naren
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > *Dr. Narendra Nath Ghosh*
> > > >
> > > > *Research Associate*
> > > >
> > > > *University of Gour Banga*
> > > >
> > > > *Department of Chemistry*
> > > >
> > > > *Malda-732102*
> > > >
> > > > *India*
> > > >
> > > > *Phone: +919126667601*
> > >
> > > ********************************************************
> > > - Article premier - Les hommes naissent et demeurent
> > > libres et Ã©gaux en droits. Les distinctions sociales
> > > ne peuvent Ãªtre fondÃ©es que sur l'utilitÃ© commune
> > > - Article 2 - Le but de toute association politique
> > > est la conservation des droits naturels et
> > > imprescriptibles de l'homme. Ces droits sont la libertÃ©,
> > > la propriÃ©tÃ©, la sÃ»retÃ© et la rÃ©sistance Ã  l'oppression.
> > > ********************************************************
> > >
> > >    Giuseppe Mattioli
> > >    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> > >    v. Salaria Km 29,300 - C.P. 10
> > >    I 00015 - Monterotondo Stazione (RM), Italy
> > >    Tel + 39 06 90672342 - Fax +39 06 90672316
> > >    E-mail: <giuseppe.mattioli at ism.cnr.it>
> > >    http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
> > >    ResearcherID: F-6308-2012
> > >
> > > _______________________________________________
> > > 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 égaux en droits. Les distinctions sociales
> ne peuvent être fondées que sur l'utilité commune
> - Article 2 - Le but de toute association politique
> est la conservation des droits naturels et
> imprescriptibles de l'homme. Ces droits sont la liberté,
> la propriété, la sûreté et la résistance à l'oppression.
> ********************************************************
>
>    Giuseppe Mattioli
>    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
>    v. Salaria Km 29,300 - C.P. 10
>    I 00015 - Monterotondo Stazione (RM), Italy
>    Tel + 39 06 90672342 - Fax +39 06 90672316
>    E-mail: <giuseppe.mattioli at ism.cnr.it>
>    http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
>    ResearcherID: F-6308-2012
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20170421/8b439ce2/attachment.html>