[Pw_forum] Fw: band structure issue
Giovanni Cantele
giovanni.cantele at spin.cnr.it
Wed Jan 27 11:16:46 CET 2016
Because the image resolution is extremely low, could you please explain what are the green and red curve in Fig. 3? Moreover, it is not really clear
what are these extra states of the 2x2x2 supercell you are worried about and why you think that the Siesta calculations are accurate, whereas those with QE are not.
By looking, for example, at the A-Z path of the band structure of the 1x1x1 cell (left panel of Figs. 1 and 2), it actually seems to me that even in this case the QE calculation has “more” states than SIESTA (5 bands versus three in the range 1-4 eV, if I correctly understand), and the correct result is the QE one! (compare with literature results).
Giovanni
>
> On 26 Jan 2016, at 08:31, Tariq Sami <tariq.sami72 at yahoo.com> wrote:
>
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>
>
>
> On Thursday, January 14, 2016 3:49 PM, Tariq Sami <tariq.sami72 at yahoo.com> wrote:
>
>
>
> Hello dear QE users,
> I'm using Quantum espresso-5.2.0 for the calculation of band structure of rutile TiO2. While doing my calculations for single cell using
>
>
> &control
> calculation = 'scf',
> prefix = 'tio',
> verbosity = 'default',
> outdir = './' ,
> pseudo_dir = '/home/sami_QU/espresso-5.2.0/pseudo',
>
> /
> &system
> ibrav = 6,
> celldm(1) = 8.680890966,
> celldm(3) = 0.64394729330137,
> nat = 6,
> ntyp = 2,
> ecutwfc = 40,
> ecutrho = 300,
> occupations = 'tetrahedra',
> smearing ='mp',
> degauss= 0.02 ,
> /
> &electrons
> conv_thr = 1.0e-09,
> electron_maxstep = 100,
> mixing_beta = 0.3,
> conv_thr = 1.0e-08,
> mixing_mode = 'plain',
> /
>
> ATOMIC_SPECIES
> O 15.999 O.pz-nc.UPF
> Ti 47.867 Ti.pz-n-nc.UPF
> ATOMIC_POSITIONS (alat)
> Ti 0.00000000 0.00000000 0.00000000
> Ti 0.50000000 0.50000000 0.32197370
> O 0.30530000 0.30530000 0.00000000
> O -0.30530000 -0.30530000 0.00000000
> O 0.80530010 0.19470000 0.32197370
> O 0.19470000 0.80530010 0.32192370
> K_POINTS (automatic)
> 3 3 6 1 1 1
> my results are some what consistent with the previous studies ,but when i do the same calculations for 2x2x2 supercell using
> /
> &system
> ibrav = 6,
> celldm(1) = 17.36178193,
> celldm(3) = 0.64394729330137,
> nat = 48,
> ntyp = 2,
> ecutwfc = 40,
> ecutrho = 300,
> occupations = 'tetrahedra',
> smearing ='mp',
> degauss= 0.02 ,
> /
> &electrons
> conv_thr = 1.0e-09,
> electron_maxstep = 100,
> mixing_beta = 0.3,
> conv_thr = 1.0e-08,
> mixing_mode = 'plain',
> /
>
> ATOMIC_SPECIES
> O 15.999 O.pz-nc.UPF
> Ti 47.867 Ti.pz-n-nc.UPF
> ATOMIC_POSITIONS (alat)
> Ti 0.00000000 0.00000000 0.00000000
> Ti 0.25000000 0.25000000 0.16098685
> O 0.15265000 0.15265000 0.00000000
> O -0.15265000 -0.15265000 0.00000000
> O 0.40265005 0.09735000 0.16986850
> O 0.09735000 0.40265005 0.16986850
> Ti 0.50000000 0.00000000 0.00000000
> Ti 0.75000000 0.25000000 0.16098685
> O 0.65265000 0.15265000 0.00000000
> O 0.34735000 -0.15265000 0.00000000
> O 0.90265005 0.09735000 0.16986850
> O 0.59735000 0.40265005 0.16986850
> Ti 0.00000000 0.50000000 0.00000000
> Ti 0.25000000 0.75000000 0.16098685
> O 0.15265000 0.65265000 0.00000000
> O -0.15265000 0.34735000 0.00000000
> O 0.40265005 0.59735000 0.16986850
> O 0.09735000 0.90265005 0.16986850
> Ti 0.50000000 0.50000000 0.00000000
> Ti 0.75000000 0.75000000 0.16098685
> O 0.65265000 0.65265000 0.00000000
> O 0.34735000 0.34735000 0.00000000
> O 0.90265005 0.59735000 0.16986850
> O 0.59735000 0.90265005 0.16986850
> Ti 0.00000000 0.00000000 0.32197370
> Ti 0.25000000 0.25000000 0.48296055
> O 0.15265000 0.15265000 0.32197370
> O -0.15265000 -0.15265000 0.32197370
> O 0.40265005 0.09735000 0.48296055
> O 0.09735000 0.40265005 0.48296055
> Ti 0.50000000 0.00000000 0.32197370
> Ti 0.75000000 0.25000000 0.48296055
> O 0.65265000 0.15265000 0.32197370
> O 0.34735000 -0.15265000 0.32197370
> O 0.90265005 0.09735000 0.48296055
> O 0.59735000 0.40265005 0.48296055
> Ti 0.00000000 0.50000000 0.32197370
> Ti 0.25000000 0.75000000 0.48296055
> O 0.15265000 0.65265000 0.32197370
> O -0.15265000 0.34735000 0.32197370
> O 0.40265005 0.59735000 0.48296055
> O 0.09735000 0.90265005 0.48296055
> Ti 0.50000000 0.50000000 0.32197370
> Ti 0.75000000 0.75000000 0.48296055
> O 0.65265000 0.65265000 0.32197370
> O 0.34735000 0.34735000 0.32197370
> O 0.90265005 0.59735000 0.48296055
> O 0.59735000 0.90265005 0.48296055
>
> K_POINTS (automatic)
> 3 3 6 1 1 1
>
>
> there are some extra states , as in Fig[1]. The same test calculations when done using siesta gives accurate results Fig. [2].A comparison of Dos of the cell and supercell using siesta and Qe respectively is shown in the Fig[3]. Actually i'm a new QE user , so can anyone please help me out in this regard
> I look forward to your suggestion! Thank you!
>
> SAMI TARIQ
> MPHILL CANDIDATE
> DEPARTMENT OF PHYSICS
> QUAID E AZAM UNIVERSITY, ISLAMABAD
> PAKISTAN
>
>
> <Selection_193.png><Selection_194(1).jpg><Selection_195.jpg>_______________________________________________
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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: http://people.na.infn.it/~cantele
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