[Pw_forum] Si diamond-cubic to beta-Sn transformation
On Oct 8, 2010, at 22:05 , Daryl Chrzan wrote: > I still believe that there are 2 atoms per unit cell in the beta-Sn > structure, so I am a bit confused by your final statement > don't take it too seriously: I interpreted the "4a" positions mentioned in http://cst-www.nrl.navy.mil/lattice/struk/a5.html as meaning that there are 4 atoms in the unit cell, but I am too lazy to go and check the International Tables of Cristallography! P. --- Paolo Giannozzi, Dept of Chemistry&Physics, Univ. Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
[Pw_forum] Si diamond-cubic to beta-Sn transformation
Not quite: celldm(1) =11.15433936, celldm(3) =0.54170527 On 10/08/2010 03:55 PM, Daryl Chrzan wrote: > Michael, > > Thank you for the response. I agree that I am far from the minimum. > However, when I do get to the minimum, I end up with a c/a ratio that is far > off, and an energy difference of 0.6 eV, about twice what you find. (I have, > I believe, accounted for the proper number of atoms, etc.) > > I have done the calculation with the PAW potential and the PZ-vbc potential > and obtained the same results. Obviously I am doing something wrong but I > simply cannot see it. I'll try the Si.pbe-n-van.UPF and see if I can > reproduce your 0.29 eV energy difference. Did you c/a work out to be around > 0.547? > > Daryl -- Michael J. Mehl Head, Center for Computational Materials Science Naval Research Laboratory Code 6390 Washington DC
[Pw_forum] plot the wave functions
Dear developers and users: How can I get the wave functions of top valence band and bottom conduction band? I want to plot the functions at some special points like gamma. Thanks! S.D.Wang -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20101008/15af4a5b/attachment.htm
[Pw_forum] plot the wave functions
use the post processing program pp.x. for the input you can use something like this: &INPUTPP prefix='Ge64-k8', outdir='/home/jfbinder/Ge/xps/cube8/temp/' filplot = 'wave.dat', plot_num = 7, kpoint = 1, kband=294, lsign=.true. / &PLOT nfile = 1, fileout = 'wave.cube', iflag = 3, output_format = 6, / shudong wang wrote: > Dear developers and users: > How can I get the wave functions of top valence band and bottom > conduction band? I want to plot the functions at some special points > like gamma. > > Thanks! > > S.D.Wang > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
[Pw_forum] Si diamond-cubic to beta-Sn transformation
Paolo, The smearing flag solved the problems. Thank you much for the tip (on behalf of myself and my class). I agree this is an excellent teaching exercise. Mark Asta suggested it to me, and it seems perfect. I still believe that there are 2 atoms per unit cell in the beta-Sn structure, so I am a bit confused by your final statement. I suppose this depends on the choice of lattice vectors... Daryl Daryl C. Chrzan Professor, Materials Science and Engineering University of California Berkeley, CA 94720 and Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley, CA 94720 ph./fax: 510 643 1624
[Pw_forum] Negative rho is large
Dear All QE users
I am doing caclulation for ZrO2 monoclinic phase. In scf calculation I
took ecutwfc=75 Ry and ecut_rho=750. I am getting message negative
rho up down 0.261e0.00 0.00 in output. i have used ultrasoft pseudo
potential. how to improve my result.
Here I paste my input scf file.
&control
calculation='scf'
restart_mode='from_scratch',
tstress = .true.
tprnfor = .true.
prefix='zro',
pseudo_dir = '/home/mayank/pseudo/',
outdir='/home/mayank/tmp2/'
/
&system
ibrav=12 ,celldm(1)=10.0928877,celldm(2)=0.967796293,celldm(3)=0.979591837,
celldm(4)=-0.16074,celldm(5)=0.0,celldm(6)=0.0, nat=12 ,
ntyp=2,
ecutwfc= 75.
ecutrho=750
/
&electrons
conv_thr=1.0D-8
mixing_beta=0.3
diagonalization='david'
/
&ions
/
ATOMIC_SPECIES
Zr 91.22 Zr.pw91-nsp-van.UPF
O 15.99 O.pw91-van_ak.UPF
ATOMIC_POSITIONS {crystal}
Zr 0.209735100 0.276043346 0.042234007
Zr 0.290264900 0.723956654 0.542234007
Zr 0.790264900 0.723956654 0.957765993
Zr 0.709735100 0.276043346 0.457765993
O0.344714661 0.068493659 0.332481802
O0.155285339 0.931506341 0.832481802
O0.655285339 0.931506341 0.667518198
O0.844714661 0.068493659 0.167518198
O0.478408144 0.449572291 0.757453977
O0.021591856 0.550427709 0.257453977
O0.521591856 0.550427709 0.242546023
O0.978408144 0.449572291 0.742546023
K_POINTS automatic
4 4 4 1 1 1
Thanks
--
Mayank kumar gupta
Contact No- 9869834437
? ? ? ? ? ? ? ? ? 8097400037
? ? ? ? ? ? ? ? ?8080458227
[Pw_forum] Si diamond-cubic to beta-Sn transformation
Michael, Thank you for the response. I agree that I am far from the minimum. However, when I do get to the minimum, I end up with a c/a ratio that is far off, and an energy difference of 0.6 eV, about twice what you find. (I have, I believe, accounted for the proper number of atoms, etc.) I have done the calculation with the PAW potential and the PZ-vbc potential and obtained the same results. Obviously I am doing something wrong but I simply cannot see it. I'll try the Si.pbe-n-van.UPF and see if I can reproduce your 0.29 eV energy difference. Did you c/a work out to be around 0.547? Daryl Daryl C. Chrzan Professor, Materials Science and Engineering University of California Berkeley, CA 94720 and Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley, CA 94720 ph./fax: 510 643 1624
[Pw_forum] Si diamond-cubic to beta-Sn transformation
Daryl Chrzan wrote: > smearing = 'gaussian', > degauss = 0.02, you need occupations='smearing' as well, or else the code will silently default to fixed occupations. There should be a check and a warning, but there isn't any. Using QE in teaching is a great way to find all kinds of problems. I noticed it because this statement looked weird to me: highest occupied, lowest unoccupied level (ev):11.4054 5.2182 and no, the numbers were not printed in revers order. It doesn't make any difference for diamond Si, but it does for beta-Sn Si. I got betatin.out:!total energy = -19.20675112 Ry diamond.out:!total energy = -19.25371607 Ry i.e. 0.32eV/atoms > Beta-Sn: > nat=2 I was convinced that beta-Sn has 4 atoms per unit cell, not 2. I am interested because I also have used QE for teaching, and the diamond to beta-tin transition is a good exercise Paolo -- Paolo Giannozzi, Democritos and University of Udine, Italy
