Dear Naren, Increase ecut. Use more intense kpoint mesh. On Apr 21, 2017 4:50 PM, "Giuseppe Mattioli" <[email protected]> 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: <[email protected]> > http://www.ism.cnr.it/en/staff/giuseppe-mattioli/ > ResearcherID: F-6308-2012 > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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