> On 05 Jul 2015, at 18:29, Gul Rahman <[email protected]> wrote:
>
> Dear All,
> I am doing some test calculations on 2D Sn and comparing QE with SIESTA. Both
> QE and SIESTA almost give the same results (DOS, lattice constnat, charge,,).
> However, I have problem with the band structure. I want to plot the band
> structure in
> 0.0,0.0 0.0 to 0.33,0.330.00 to 0.5,0.0,0.0.
> I either write a python code or jut do by hand to put the number of points in
> the input file for the band structure calculation.
> _POINTS crystal
> 29
> 0.00000 0.00000 0.00000 1.0000
> 0.03000 0.03000 0.00000 1.0000
> 0.06000 0.06000 0.00000 1.0000
> 0.09000 0.09000 0.00000 1.0000
> 0.12000 0.12000 0.00000 1.0000
> 0.15000 0.15000 0.00000 1.0000
> 0.18000 0.18000 0.00000 1.0000
> 0.21000 0.21000 0.00000 1.0000
> 0.24000 0.24000 0.00000 1.0000
> 0.27000 0.27000 0.00000 1.0000
> 0.30000 0.30000 0.00000 1.0000
> 0.33000 0.33000 0.00000 1.0000
> 0.34000 0.31060 0.00000 1.0000
> 0.35000 0.29120 0.00000 1.0000
> 0.36000 0.27180 0.00000 1.0000
> 0.37000 0.25240 0.00000 1.0000
> 0.38000 0.23300 0.00000 1.0000
> 0.39000 0.21360 0.00000 1.0000
> 0.40000 0.19420 0.00000 1.0000
> 0.41000 0.17480 0.00000 1.0000
> 0.42000 0.15540 0.00000 1.0000
> 0.43000 0.13600 0.00000 1.0000
> 0.44000 0.11660 0.00000 1.0000
> 0.45000 0.09720 0.00000 1.0000
> 0.46000 0.07780 0.00000 1.0000
> 0.47000 0.05840 0.00000 1.0000
> 0.48000 0.03900 0.00000 1.0000
> 0.49000 0.01960 0.00000 1.0000
> 0.50000 0.00020 0.00000 1.0000
>
> when I used it, I always see crossing points in the band structure. Pls, see
> the attached file and you can see crossing points not only around Dirac
> point, but also above that.
> Could you plz let me know why I am facing this problem whenever I try the
> band structure of any material and I will have these crossing lines.
Are you referring to the crossings around -1.5 and + 1.5 eV? These are just
spurious, and are due to the fact that because consecutive points are connected
in the plot, if the ordering of the bands is not the proper one, a point in a
lower bands is connected not to the next point in the same band but to a point
in a higher band. Plotting the band structure only with points or calculating
the band structure with a larger number of k-points solves the problem,
Other crossings (e.g. around 4 eV) are instead the results of the calculation,
so if you do not expect them it means that your input files do contain some
error (e.g. k-points coordinates).
>
> Is there any option in QE for calculating these points by just giving the
> high symmetry points in the input for band structure calculations.
Yes, with the latest version. You can specify a k-point path as follows:
K_POINTS { crystal_b }
5
gG 50
M 50
X 50
R 50
gG 1
which corresponds to 5-1=4 lines in the Brillouin zone of a simple cubic
lattice, that s, Gamma-M, M-X, X-R, R-Gamma, each sampled with 50 points. The
point labels that are recognised are shown in detail in
espresso-5.2.0/Doc/brillouin_zones.pdf
Giovanni
> Thanks,
> Gul
>
> --
>
> Dr. Gul Rahman
> Assistant Professor,
> Department of Physics,
> Quaid-i-Azam University,
> Islamabad, Pakistan
> http://www.qau.edu.pk/profile.php?id=818020
> <http://www.qau.edu.pk/profile.php?id=818020><bands.ps>_______________________________________________
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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: [email protected]
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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