[QE-users] convergence problem for a molecule

Dr. K. C. Bhamu kcbhamu85 at gmail.com
Thu Jan 7 10:45:01 CET 2021


Dear Dr. Giuseppe
You suggestion worked for me.
     "occupations='smearing', smearing='gaussian', degauss=0.01,"
The structure even converged when I excluded the vdw_corr tag.

Thank you very much
Bhamu



On Tue, Jan 5, 2021 at 11:48 PM Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> Dear K C Bhamu
> When you simulate molecules having a large amount of rotational
> degrees of freedom, I recommend to use first a tight-binding or
> empirical tool to explore configurations, to avoid high-energy
> structures. The following one is excellent, very easy to use and very
> fast to run.
>
> https://xtb-docs.readthedocs.io/en/latest/contents.html
>
> This said, your starting configuration was trapped in an unfortunate
> structure where two sp2 C atoms (numbers 33 and 35) were twisted
> instead of being planar. You probably removed two H atoms from sp3
> atoms without relaxing them. The following structure, simply optimized
> with a force-field, should not give problems (but I have not run the
> calculation...).
>
> 45
>          Energy:      52.7144978
> H          8.48608       10.45663       13.88529
> C         10.12285       10.35161       10.80715
> H          9.75081        9.36965       10.43974
> C         11.49997       10.08512       11.39597
> H         12.30756        9.85722       10.70499
> C         11.75878       10.11652       12.72470
> C         10.64679       10.32692       13.74405
> H         10.74317        9.58583       14.56637
> H         10.73789       11.33550       14.19281
> C          9.24848       10.13193       13.14479
> H          9.07291        9.05796       12.91129
> C          9.14194       10.92818       11.85742
> H          8.10293       10.88215       11.46867
> H          9.38712       11.98966       12.08748
> C          8.94637       11.52201        8.84268
> C         10.25893       11.30287        9.59702
> H          9.13189       12.17491        7.96386
> H          8.19218       12.02297        9.48301
> H          8.54193       10.55155        8.48460
> H         10.65844       12.28636        9.92936
> H         10.98302       10.86213        8.87653
> C         13.17440        9.88279       13.22285
> H         13.11888        9.04537       13.95078
> H         13.83707        9.54798       12.39520
> C         15.69736       11.92481       15.44478
> H         16.74498       11.70891       15.74860
> H         15.07047       11.97162       16.36387
> C         15.58617       13.25420       14.70482
> H         16.14427       13.14997       13.74597
> C         14.09237       13.52300       14.41126
> H         14.03472       14.35009       13.67327
> H         13.54419       13.83190       15.32752
> C         13.36446       12.32498       13.84523
> C         13.87547       11.06693       13.87464
> C         15.21374       10.78810       14.53332
> H         15.14294        9.87981       15.16991
> H         15.94984       10.58575       13.72543
> C         16.23591       15.73576       14.79615
> C         16.23058       14.39236       15.52642
> H         16.75074       16.49369       15.42343
> H         15.20340       16.09456       14.60831
> H         16.77780       15.64679       13.83071
> H         15.70219       14.50766       16.49821
> H         17.28870       14.12285       15.73764
> H         12.40535       12.52093       13.38556
>
> Finally,
>
> >   occupations='smearing',
> >   smearing='mv',
> >   degauss=0.005d0,
>
> This is just a fine way for me to calculate a bunch of unoccupied
> molecular orbitals, but there is no need to use 'mv', which is for
> metals and less stable than 'gaussian', suitable for an "insulator"
> such as your molecule. I would use instead
>
>      occupations='smearing', smearing='gaussian', degauss=0.01,
>
> HTH
> Giuseppe
>
>
> Quoting "Dr. K. C. Bhamu" <kcbhamu85 at gmail.com>:
>
> > Dear QE Users
> > I wish you all a very happy new year 2021!
> >
> > I am running a molecule  with QE_6.6  but facing a convergence problem.
> > I tried with and without 'local-TF' and both the options are not working.
> >
> > Could someone please have a look and suggest to me any solution?
> >
> >
> > &CONTROL
> >                  calculation = 'relax'
> >                 restart_mode = 'from_scratch'
> >                       outdir = './tmp'
> >                   pseudo_dir = '/home/kcbhamu/PPs'
> >                       prefix = 'pwscf'
> > !                     disk_io = 'none'
> >                    verbosity = 'default'
> >                etot_conv_thr = 0.0001
> >                forc_conv_thr = 0.001
> >                        nstep = 400
> >                      tstress = .true.
> >                      tprnfor = .true.
> >  /
> >
> > &SYSTEM
> >   ibrav=1,
> >   celldm(1)=47.2431531141d0,
> >   nat=45,
> >   ntyp=2,
> >   ecutwfc=65,
> >   ecutrho=650,
> >   occupations='smearing',
> >   smearing='mv',
> >   degauss=0.005d0,
> >  vdw_corr = 'DFT-D3'
> >  assume_isolated='mt'
> > /
> >
> > &ELECTRONS
> > electron_maxstep=999
> >   conv_thr=1d-06,
> >   mixing_beta=0.2,
> > mixing_mode='local-TF'
> >
> >  /
> > &IONS
> >                 ion_dynamics = 'bfgs'
> >  /
> >
> > ATOMIC_SPECIES
> >     C   12.0107000000  C.pbe-n-rrkjus_psl.1.0.0.UPF
> >     H    1.0079000000  H.pbe-rrkjus_psl.1.0.0.UPF
> >
> >
> > ATOMIC_POSITIONS {crystal}
> >    H   0.3386670148d0   0.4101931225d0   0.5567254731d0
> >    C   0.4036222773d0   0.4149138472d0   0.4333448459d0
> >    H   0.3896346255d0   0.3765041141d0   0.4161167921d0
> >    C   0.4581434036d0   0.4058061800d0   0.4574431361d0
> >    H   0.4912475090d0   0.4017946150d0   0.4290030859d0
> >    C   0.4691277774d0   0.4031817060d0   0.5099401207d0
> >    C   0.4253264110d0   0.4071145213d0   0.5513729998d0
> >    H   0.4327529164d0   0.3774401630d0   0.5831675023d0
> >    H   0.4276381009d0   0.4464313224d0   0.5714430496d0
> >    C   0.3695729050d0   0.3993621172d0   0.5273547231d0
> >    H   0.3636345597d0   0.3567170026d0   0.5178739313d0
> >    C   0.3632663685d0   0.4323236400d0   0.4762330101d0
> >    H   0.3222111650d0   0.4290965819d0   0.4608472936d0
> >    H   0.3700270318d0   0.4749720278d0   0.4855397879d0
> >    C   0.3550607872d0   0.4623307485d0   0.3556503474d0
> >    C   0.4072533598d0   0.4549686753d0   0.3866434814d0
> >    H   0.3606425820d0   0.4892876373d0   0.3214193048d0
> >    H   0.3233410756d0   0.4794322728d0   0.3807732671d0
> >    H   0.3403880199d0   0.4238800875d0   0.3400782741d0
> >    H   0.4209431037d0   0.4937648655d0   0.4025522295d0
> >    H   0.4387880407d0   0.4413449118d0   0.3590270889d0
> >    C   0.5253811195d0   0.3963553146d0   0.5303629030d0
> >    H   0.5275121376d0   0.3597814346d0   0.5550954410d0
> >    H   0.5527498198d0   0.3902494747d0   0.4963382387d0
> >    C   0.6241002137d0   0.4781543529d0   0.6196978697d0
> >    H   0.6647510385d0   0.4689076884d0   0.6339462788d0
> >    H   0.5991190333d0   0.4830564471d0   0.6558173241d0
> >    C   0.6245138950d0   0.5312336801d0   0.5887880064d0
> >    H   0.6519223460d0   0.5264394769d0   0.5543229817d0
> >    C   0.5684449407d0   0.5426728657d0   0.5664333374d0
> >    H   0.5687315910d0   0.5794127480d0   0.5422455469d0
> >    H   0.5411292134d0   0.5502889434d0   0.6003493599d0
> >    C   0.5467291274d0   0.4961698023d0   0.5329872592d0
> >    H   0.5063039439d0   0.5054115901d0   0.5182523433d0
> >    C   0.5462494021d0   0.4434602904d0   0.5642948220d0
> >    C   0.6023141698d0   0.4317080266d0   0.5862549648d0
> >    H   0.6016470576d0   0.3946830496d0   0.6101287345d0
> >    H   0.6295099445d0   0.4241153738d0   0.5522682608d0
> >    C   0.6550325759d0   0.6297412310d0   0.5941577656d0
> >    C   0.6461033707d0   0.5769127641d0   0.6236837684d0
> >    H   0.6727321964d0   0.6599556430d0   0.6206848621d0
> >    H   0.6175101186d0   0.6464185973d0   0.5785534114d0
> >    H   0.6823409744d0   0.6243625417d0   0.5600843513d0
> >    H   0.6183422352d0   0.5832463756d0   0.6574159578d0
> >    H   0.6841825362d0   0.5638719462d0   0.6416905666d0
> >
> > K_POINTS (gamma)
> >
> >
> >
> > Thank you very much
> > K C Bhamu
> > University of Ulsan
> > ROK
>
>
>
> GIUSEPPE MATTIOLI
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
> Mob (*preferred*) +39 373 7305625
> Tel + 39 06 90672342 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
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