[QE-users] Fe (110) slab isn't converging
Giovanni Cantele
giovanni.cantele at spin.cnr.it
Thu Feb 10 12:30:25 CET 2022
Dear Omer,
first of all a small notice, usually users writing to this forum are requested to sign e-mail, together with affiliation.
This being said, few remarks about your input:
1) you should carefully check (and visualise, using e.g. XcrysDen) your structure and lattice vectors. While
your structure does not look unreasonable (as it would be in the case in which, for example, two different atoms
were overlapped), it does not seem at a first glance a (110) surface deriving from the bulk Fe
crystal. Atoms look irregularly placed in space and a side view shows different spaced lattice planes. While this can be
“the right structure” after a relaxation of the slab, it would be better to have a look to your “starting structure” (that
derived from the crystal with no relaxation of atoms), to check if it is correct.
2) also the lattice vectors need to be checked :
> 7.4474000931 0.0000000000 0.0000000000
> 2.4824640508 7.0214770799 0.0000000000
These two vectors have an angle of 70 degrees, is that what you expect?
3) any reason why, at least at a first step, to include vdw_corr? Is vdW correction really important for your system?
4) from the QE web site I can look into Fe.pbe-spn-kjpaw_psl.1.0.0.UPF pseudo potential that should be similar to yours,
but generated within a more recent release of PS library. I read
Suggested minimum cutoff for wavefunctions: 71. Ry
Suggested minimum cutoff for charge density: 496. Ry
As such, the suggested cutoff is more than twice than yours, and the ratio between ecutrho and ecutwfc is about 7, but in your case
I see only a ratio of 5. While this parameters could have nothing to do with your convergence issues, I would carefully check the convergence of
the calculated properties with respect to them, you could easily fall into a wrong-result potential well!
5) also you should check that the choice of atoms to keep fixed during relaxation is reasonable
6) once all checks have been done, should you system be particularly tricky, you might consider to reduce mixing_beta to 0.1 or less, at least in the first
relaxation steps.
Giovanni
> On 10 Feb 2022, at 11:41, Omer Mutasim via users <users at lists.quantum-espresso.org> wrote:
>
> Dear all
> I tried to relax Fe (110) slab , but it doesn't converge. It takes very long time even though it is small slab with only 45 atoms.
> I tried f-d, m-p smearing but to no avail.
> Can you help me please ? to know what is wrong with my input file attached below:
>
> &CONTROL
> calculation = "relax"
> prefix = 'x'
> outdir = '/scratch'
> pseudo_dir = '/xx/'
> !restart_mode = 'restart'
> forc_conv_thr = 1.0e-03
> etot_conv_thr = 1e-04
> nstep = 9999
>
> /
>
> &SYSTEM
> ibrav = 0
> ecutrho = 150
> ecutwfc = 30
> nat = 45
> ntyp = 1
> occupations ='smearing' , smearing='f-d' , degauss=0.005
> vdw_corr = 'DFT-D3'
> nspin = 2
> starting_magnetization(1) = 0.1
> /
> &ELECTRONS
> conv_thr = 1e-06
> electron_maxstep = 9999
> mixing_mode ='local-TF'
> mixing_beta = 0.3
> /
>
> &IONS
> /
>
> K_POINTS {automatic}
> 2 2 1 0 0 0
>
> ATOMIC_SPECIES
> Fe 55.845 Fe.pbe-spn-kjpaw_psl.0.2.1.UPF
> CELL_PARAMETERS {angstrom}
> 7.4474000931 0.0000000000 0.0000000000
> 2.4824640508 7.0214770799 0.0000000000
> 0.0000000000 0.0000000000 25.1350002289
> ATOMIC_POSITIONS (angstrom)
> Fe 5.5818789877 2.5026591675 10.5421792561 0 0 0
> Fe 4.1125866520 4.8151882619 10.6772393880
> Fe 2.1958530690 7.2414707420 10.3206255931
> Fe 1.1033564060 1.9504258780 0.0000000000 0 0 0
> Fe 1.1240846033 1.9239546627 4.4015746387
> Fe 0.5929191720 2.2727761723 9.2300878464 0 0 0
> Fe 1.9418633362 0.7673280599 2.1503683749
> Fe 1.8505911190 0.7816285240 6.8697562640
> Fe 3.5857982640 1.9504258780 0.0000000000 0 0 0
> Fe 3.6010156782 2.0356057803 4.4040536951
> Fe 3.3892107507 2.4333408596 9.2315052153 0 0 0
> Fe 4.4107991582 0.7671459373 2.2844419078
> Fe 4.3403612910 0.9089118831 6.8687340519
> Fe 6.0682401770 1.9504258780 0.0000000000 0 0 0
> Fe 6.0921186925 1.9492701251 4.5081309218
> Fe 6.8957462620 0.7801563310 2.0268864960 0 0 0
> Fe 6.8261914569 0.9046029160 6.7661838994
> Fe 1.8724868770 4.4014805858 -0.2143812725
> Fe 1.8485507821 4.2994702275 4.3824953904 0 0 0
> Fe 1.8240284641 4.7344494204 9.2345798280
> Fe 2.7582676160 3.1206253240 2.0268864960 0 0 0
> Fe 2.6683169740 3.1739888190 6.8797363658
> Fe 4.3474449433 4.3631009861 -0.1911888976
> Fe 4.3246850209 4.4213381253 4.3668090656 0 0 0
> Fe 5.2753804683 3.1017230426 2.1588431075
> Fe 5.1435681580 3.2467521647 6.6302721725 0 0 0
> Fe 6.8866553226 4.2727158920 -0.2151129276
> Fe 6.8148177194 4.3601995734 4.3973105493
> Fe 6.4979897094 4.6088015071 9.2447583930 0 0 0
> Fe 7.7586179448 3.1003648378 2.1698200674
> Fe 7.6317422302 3.2430726605 6.8687193850 0 0 0
> Fe 2.7205563083 6.7460510219 -0.2000658247
> Fe 2.7608454757 6.6172987829 4.5215696688
> Fe 3.5857721560 5.4611644180 2.0268864960 0 0 0
> Fe 3.6115378719 5.4595736549 6.6122865627
> Fe 5.2407577750 6.6313638640 0.0000000000 0 0 0
> Fe 5.2548206739 6.7098271636 4.3861096452
> Fe 4.8691076063 6.9050837980 9.2329583714
> Fe 6.0682884220 5.4611644180 2.0268864960 0 0 0
> Fe 6.1028694761 5.5498338413 6.8798135598
> Fe 7.7231996880 6.6313638640 0.0000000000 0 0 0
> Fe 7.7426438544 6.6251084192 4.3864901090
> Fe 7.3977446239 6.9684054207 9.2402605725
> Fe 8.5507305580 5.4611644180 2.0268864960 0 0 0
> Fe 8.6014581434 5.5444835700 6.8763383415
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--
Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74
ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home
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