[Pw_forum] Convergence problem with Pb180Se180 Cluster optimization
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Fri Apr 21 15:45:59 CEST 2017
> 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 didn’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
> > >
> > > ……………………………………………………
> >
> > ………….
> >
> > > 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 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
********************************************************
- 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
More information about the users
mailing list