[Wien] pdos for restricted k-range or in restricted space

Sun Sep 1 04:36:12 CEST 2019

Dear All:

I would like to propose steps to produce PDOS on a k path without 
programming, but with some caveats:
- Gaussian broadening is used instead of the tetrahedron mesh;
- Weights are arbitrary, therefore the DOS scale is also arbitrary.

1) Run normal SCF (I did it for Si) and get PDOS on a regular mesh (see 
attached Si-DOS.png).

2) Save the calculation
	$ save_lapw -d SCF

3) Lunch xcrysden, select k path (e.g., G-L) with 300 intermediate 
points and save as Si.klist_band
Actually it produced 301 points, which will be important later.

4) Get eigenvalues and projections for the k points on the path:
	$ x lapw1 -band
	$ x lapw2 -band -qtl

5) In wien2web > Tasks > DOS
Configure Si.int file with "total 1 tot,s,p"

6) Edit Si.int (Energy ranges, Gaussian broadening, and magnitude of the 
broadening):
Si             #Title
-1 0.002 1 0.003   #Emin, DE, Emax, Gauss-Broad
   4   G   0.003                 #Number of DOS-cases,G/L/B broadening (Ry)
      0 1 total-DOS
      1 1 tot-Si1
      1 2 s-Si1
      1 3 p-Si1
SUM: 0 2          # NUMBER OF SUMMATIONS, max-nr-of summands
2 5               # this sums dos-cases 2+5 from the input above

7) Copy k list (Gaussian broadening needs Si.klist)
	$ cp Si.klist_band Si.klist

8) Unfortunately, xcrysden produces k list file that is not compatible 
with the fixed formal (50x,f5.1) used in Wien2k to read weight. To fix 
this we need to displace the weights column such that the decimal point 
is at position 54. Hints how to do it with vim editor are here 
(http://vim.1045645.n5.nabble.com/Shift-column-right-by-spaces-td5162953.html). 
There is a sample of the Si.klist file after editing:
GAMMA         0    0    0  600                      2.0 -8.00 8.00
               1    1   -1  600                      2.0
               2    2   -2  600                      2.0
...

9) Edit Si.kgen (change number of k-points to 301, which is in the first 
line). Position the number keeping in mind that the file might require 
to maintain a fixed format:
        301        76  3.255208333333E-04       101         1

10) Now we can run
	$ x tetra
and use standard plotting tools for PDOS.
The plot is attached Si-DOS-gaussian-301kpts-path-G-L.png

Note: We should keep in mind that the scale "DOS (States/eV)" has an 
arbitrary factor related to an uncertainty in the weights of k-points. 
You can also note that the total DOS in Si-DOS.png is less in magnitude 
than in Si-DOS-gaussian-301kpts-path-G-L.png, which in unphysical and 
related to the arbitrariness of weights. Since those k points are not a 
subset of the regular mesh, I do not think there is a way to determine 
their weights properly. Nevertheless, qualitatively the picture should 
be correct.

Any additional though are welcome :)

Best regards
Oleg

-- 
Oleg Rubel (PhD, PEng)
Department of Materials Science and Engineering
McMaster University
JHE 359, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
Email: rubelo at mcmaster.ca
Tel: +1-905-525-9140, ext. 24094
Web: http://olegrubel.mcmaster.ca

On Wed, Aug 28, 2019 at 12:00 AM Peter Blaha <pbl... at theochem.tuwien.ac.at>
wrote:

 > Not with standard wien2k tools.
 >
 > However, you can write your own little programs, eg.
 >
 > reading the case.qtl file for an arbitrary k-mesh of your choice and do
 > a "root sampling", i.e. divide your energy mesh into some intervals and
 > count the number of eigenvalues (times the multiplicity of the k-point)
 > in each E-interval. Plot the corresponding histogram.
 >
 > An alternative is to modify tetra such, that instead of summing over all
 > tetrahedra, it sums only over those involving k-points of your choice.
 > For this you need to understand the case.kgen file, which lists the
 > vertices of all tetrahedra and you select only thos which contain the
 > desired k-points.
 >
 >
 >
 > On 8/27/19 6:12 PM, Jens Biegert wrote:
 > > Dear All,
 > >
 > > I was wondering wether I can get the DOS, or better PDOS, for a
 > > specified k-path. Say, instead of an integration over the whole
 > > Brillouin zone, just (like for the bandstructure) along gamma to K to M
 > > to gamma.
 > >
 > > If not possible, can I restrict 3D k-space integration close to 
e.g. the
 > > K point such as to get the PDOS close to K?
 > >
 > > I saw some previous answers that seem to hint at this not being
 > > possible, but it was not clear to me.
 > >
 > > Best regards,
 > >
 > > Jens Biegert
 > >
 > > _______________________________________________
 > > Wien mailing list
 > > Wien at zeus.theochem.tuwien.ac.at
 > > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
 > > SEARCH the MAILING-LIST at:
 > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
 > >
 >
 > --
 >
 >                                        P.Blaha
 > 
--------------------------------------------------------------------------
 > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
 > Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
 > Email: bl... at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
 > WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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