[Pw_forum] Convergence or band-gap problem in orthorhombic CsPbBr3
Dear all!
I am currently trying to simulate the electronic properties of CsPbBr3 in its
low-temperature phase (orthorhombic; a=8.244, b=11.735, c=8.198 angstrom,
according to Stoumpos; Cryst. Growth Des. 2013); My principle plan is to follow
Radi et al. (arXiv:1405.1706v2), who have done this using Wien2k, muffin-tin
potentials. Eventually I want to continue processing this with YAMBO (doesn’t
take US PP), so I am using normcons PBE (from the standard repository).
However, the band-gap obtained is really tiny (without SOC, SOC is known to
further reduce the gap in this material); I have done the following:
1) Used the CIF file provided by stoumpos et al to create my unit cell and
double checked with xcrysden -pwi if it turns out properly
2) Tested convergence wrt. Total energy leading to a good compromise with
ecutwfc =60.0 (tested between 30 and 180 Ry) and a unshifted automatic 4x3x4
k-grid (tested up to 16x16x16).
3) Run Relax (gamma only) - scf - bands along G-X-S-R-G
The resulting band structure is in the pdf. The band gap at R is so tiny (0.x
eV) that I am not sure if applying scissors in yambo is justified. I also tried
smaller degauss and fixed occupations to not much success. If someone can spot
an obvious error in my input or has any hint how I can improve my results I
would be very grateful! Thank you in advance for your time and help!
Yours,
Chris
PS: I have also tried a VC-relax which clearly favors a shrinking cell (the
cubic phase of CsPbBr3 for example is a=5.605 A, so the Pnma cell is probably
far away from 0K - how to deal with this problem when trying to do a 300K
phase…?)
My scf input:
&control
calculation = 'scf'
restart_mode='from_scratch',
prefix='cspbbr3',
pseudo_dir = '. /pseudo/',
outdir='./'
wf_collect=.true.
verbosity='high'
/
&SYSTEM
ibrav = 8
celldm(1)= 15.5789
celldm(2)= 1.4235
celldm(3)= 0.9944
nat = 5
ntyp = 3
ecutwfc =60.0
occupations='smearing'
smearing='mp'
degauss=0.002
force_symmorphic=.true.
vdw_corr='grimme-d2'
/
&electrons
diago_full_acc=.true.,
conv_thr=1.0d-8
diagonalization='david'
electron_maxstep=300
/
ATOMIC_SPECIES
Pb 207.2 Pb.pbe-d-hgh.UPF
Cs 132.90500 Cs.pbe-sp-hgh.UPF
Br 79.90400 Br.pbe-hgh.UPF
ATOMIC_POSITIONS (crystal)
Pb 0.5 0.495569542 0.5
Cs 0.0 -0.54173 0.0
Br 0.0 0.496389920 0.5
Br 0.5 0.002099521 0.5
Br 0.5 0.496980388 0.0
K_POINTS {automatic}
4 3 4 0 0 0
My bands input
nbnd=200 ! include plenty of empty bands for yambo
And
K_POINTS {crystal_b}
5
0.00 0.00 0.00 10 !G
0.50 0.00 0.00 10 !X
0.50 0.50 0.00 10 !S
0.50 0.50 0.50 10 !R
0.00 0.00 0.00 10 !G
Christoph Wolf
Department of Materials Science and Engineering, POSTECH
RIST #3, 3152, San 31 Hyoja-dong, Nam-gu, Pohang, Kyungbuk, 790-784, Republic
of Korea
[http://home.postech.ac.kr/wp-content/themes/postech/images/mail_logo_postech30.png]
30POSTECH
bands.pdf
Description: bands.pdf
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Re: [Pw_forum] errors testing espresso 5.4.0
On Sep 5, 2016, at 6:19 PM, Fabricio Cannini wrote: > I can make some more tests if it helps, just tell me what to do. Grab this latest full snapshot of QE SVN repo I just generated http://qe-forge.org/snapshots/espresso-r12924-2016-09-07.tar.gz It contains Paolo's fixes. Feel free to try run it and give us feedback if the issue you saw still persists on the machine you run the initial tests. -- Filippo SPIGA ~ Quantum ESPRESSO Foundation ~ http://www.quantum-espresso.org ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
Re: [Pw_forum] Problem with charged defect calculation
Dear Evan, The postprocessing utility pp.x can calculate and plot the average potential as a function of x or y or z. This can help in performing the potential alignment. Regards Mostafa Youssef MIT ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
[Pw_forum] FW: About using plotproj.x 2
Dear QE experts, plotproj.x needs input data which I do not know how to provide them. Below is what it ask for " This small program is used to select the band eigenvalues whose ! wavefunctions projected on atomic wavefunctions have projections larger ! than a given threshold. It requires two input files. The first is a ! file with the band eigenvalues, written in the output of pw.x. ! The input file with the bands has the following format: ! nbnd, nks ! number of bands, number of k points ! --- blank line ! kvector coordinates ! --- blank line ! bands eigenvalues ! ... ! --- blank line ! kvector coordinates ! --- blank line ! bands eigenvalues ! ... ! ! The second file is written by the projwfc.x program with the option ! lsym=.false. ! ! The input of this program is: ! filename ! name of the file with the band eigenvalues ! filename1! name of the file with the projections ! fileout ! name of the output file where the bands are written ! threshold! see below ! ncri ! number of criterions for selecting the bands ! for each criterion ! first_atomic_wfc, last_atomic_wfc ! the band is selected if the !sum of the projections on !the atomic wavefunctions between !first_atomic_wfc and !last_atomic_wfc is larger than !threshold. The sum is done on !all criterions. filename and filename1 have been done, thank very much to stefano de gironcoli , The second question is below What are the following numbers: threshold and ncri? How can I found them? My system has 39 atoms (8 pb atoms, 4Nb atoms, 2 Mg atoms, 2 Ti atoms, and 23 O atoms). the pw.x use 328 electrons, 164 bands, 14 k-points). First I run scf and then I run nscf calculations. After that I used projwfc.x code and I got 98 files : "perfex.pdos_atm#1(Pb)_wfc#1(s)" --- "perfex.pdos_atm#39(O)_wfc#2(p)". Thank you in advance, Abdullah From: Abdullah N. Albarakati Sent: Sunday, September 04, 2016 8:34 AM To: PWSCF Forum [pw_forum@pwscf.org] Cc: a_alb...@yahoo.com Subject: About using plotproj.x Dear QE experts, plotproj.x needs input files and parameters which I do not know how to provide them. Below is what it ask for " This small program is used to select the band eigenvalues whose ! wavefunctions projected on atomic wavefunctions have projections larger ! than a given threshold. It requires two input files. The first is a ! file with the band eigenvalues, written in the output of pw.x. ! The input file with the bands has the following format: ! nbnd, nks ! number of bands, number of k points ! --- blank line ! kvector coordinates ! --- blank line ! bands eigenvalues ! ... ! --- blank line ! kvector coordinates ! --- blank line ! bands eigenvalues ! ... ! ! The second file is written by the projwfc.x program with the option ! lsym=.false. ! ! The input of this program is: ! filename ! name of the file with the band eigenvalues ! filename1! name of the file with the projections ! fileout ! name of the output file where the bands are written ! threshold! see below ! ncri ! number of criterions for selecting the bands ! for each criterion ! first_atomic_wfc, last_atomic_wfc ! the band is selected if the !sum of the projections on !the atomic wavefunctions between !first_atomic_wfc and !last_atomic_wfc is larger than !threshold. The sum is done on !all criterions. What are the following numbers: threshold and ncri? How can I found them? my system has 39 atoms (8 pb atoms, 4Nb atoms, 2 Mg atoms, 2 Ti atoms, and 23 O atoms). the pw.x use 328 electrons, 164 bands, 14 k-points). First I run scf and then I run nscf calculations. After that I used projwfc.x code and I got "perfex.pdos_atm#1(Pb)_wfc#1(s)" --- "perfex.pdos_atm#39(O)_wfc#2(p)". Thank you in advance, Abdullah This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify Email System Administrator (e_ad...@uqu.edu.sa ) . Please note that any views or opinions presented in this email are solely those of the author and do not necessarily represent those of the Umm Al-Qura University. Finally, the recipient should check this email and any attachments for the presence of viruses. The Information Technology and Technical Support Center of Umm Al-Qura University accepts no liability fo
[Pw_forum] Problem with charged defect calculation
Dear all, I am studying the charged defects in semiconductor with GGA-PBE functional. It is known that the average potentials of the charged defect calculation and that of the unperturbed host need to be aligned. My question is how to align the potential of the defect supercell with Q.E. codes, or how to obtain the the electrostatic potential as a function of the distance in the supercell. Dose any one has the experience with potential alignment in defect formation calculation with Q.E. codes? Any suggestions or comments are appreciated. Evan USC, China ___ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
