A question regarding dvscf and pp.py

[Vahid]

Dear EPW Users,

After doing the phonon calculation, QE prints many dvscf files all of which have no content except for dvscf1. So I am assuming that all dvscf values are stored in this file for all perturbations and q points and they are stored in real space (not reciprocal space). After running the pp.py code provided in the EPW phonon folder, this code copies dvscf1 to dvscf_q1, dvscf_q2 ... but these are copies of the same file. Beyond a formatting convenience, is there a reason for making so many copies of the same file?

Thank you,

Vahid

Vahid Askarpour
Department of Physics and Atmospheric Science
Dalhousie University
Halifax, NS Canada

[sponce]

Dear Vahid,

QE should print a dvscf file for each q-point. Those are binary files so you should not be able to see their content but they should have non-zero size.
The pp.py script do not copy the same file over. All the files should be different for each q-points.

You should also have one .dyn file for each q-point.

Make sure that you have put

Code: Select all

fildvscf = 'dvscf',

in your ph input file as it is what generate the files.

Best,

Samuel

[Gargee Bhattacharyya]

I am facing error while runening the scrpit python pp.py .. I am calculating superconductivity of 2 D material. Lattice parameter of my sheet is a=b=5.06 angstrom. I am using irreducible q point 6 6 1 and getting error as follows:

Enter the number of irreducible q-points
6
6
1
rm: cannot remove `_ph0/B-alpha.q_2/*wfc*': No such file or directory
rm: cannot remove `_ph0/B-alpha.q_3/*wfc*': No such file or directory
rm: cannot remove `_ph0/B-alpha.q_4/*wfc*': No such file or directory
rm: cannot remove `_ph0/B-alpha.q_5/*wfc*': No such file or directory
rm: cannot remove `_ph0/B-alpha.q_6/*wfc*': No such file or directory


Can anyone please help me in this regard ? How to give q points ?

Gargee Bhattacharyya
PhD Student
IIT Indore

[Vahid]

The number of irreducible q points is the number of phonons for which .dyn files are calculated. The list of these points is printed at the beginning of the PHONON output.
Or simply count how many .dyn files you have.

Vahid

[Gargee Bhattacharyya]

Thank You for help.

For EPW calculation , I need to run one nscf calculation. How to give K-points in nscf.in file ?

[Vahid]

In one of the earlier versions of EPW, the following Octave file is provided for generating the nscf k grid. Just run it with Octave and the file klist.dat will contain the k points. Note that this is for a 10x10x10 grid. Change the nk's as needed.

Code: Select all

nk1 = 10;
nk2 = 10;
nk3 = 10;
fid = fopen('klist.dat','w');
for i1=0:nk1-1;
 for i2=0:nk2-1;
  for i3=0:nk3-1;
    kvec = [i1/nk1 i2/nk2 i3/nk3 1/(nk1*nk2*nk3)];
    fprintf(fid,'%15.13f %15.13f %15.13f %15.13f\n',kvec');
  end;
 end;
end;
fclose(fid);

Vahid

[Gargee Bhattacharyya]

Dear Sir ,
After nscf calculation I want to run epw calculation. I have used nscf with irreducible k points as given below which was generated in the OUTCAR file (also presented in IBZKPT file). My question is what should I use as my input for dis_froz_max , proj (:) ? I am doing this calculation for 2D structure. Should I use the nk values same as the k points as I used for optimization in vasp ? What should I use for nq ? and Nkf and Nqf values ?

nk1 = 6
nk2 = 6
nk3 = 6

nq1 = 6
nq2 = 6
nq3 = 6

mp_mesh_k = .true.

nkf1 = 20
nkf2 = 20
nkf3 = 20

nqf1 = 20
nqf2 = 20
nqf3 = 20

At the last portion of epw.in file How to give K points ? I have seen the example of MgB2, SiC ... how they gave 28 or 16 cartesian k points


nscf.in file K POINTS--- (as generated in OUTCAR file)

K_POINTS cartesian
248
0.000000 0.000000 0.000000 1.000000
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0.071437 0.029906 0.000000 2.000000
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[carla.verdi]

Dear Gargee,

A few points in response to your questions:

- Please note that before running epw, the nscf calculation needs to be run using a uniform unshifted grid (crystal coordinates between 0 and 1), as you can see in the examples.

- To find out what you need for dis_froz_max , proj (:) you need to familiarize yourself with the wannierization process. The Wannier website has a very useful user guide and tutorial guide, see http://wannier.org/user_guide.html

- nq1/nq2/nq3 are the values of the coarse uniform grid used for the phonon calculation, nk1/nk2/nk3 are the values of the coarse uniform grid used for the electron (i.e. nscf) calculation

- nkf/nqf determine your arbitrary fine grid for the interpolation: it is your choice, and it will determine the convergence of the desired properties.

- In the last part of epw.in you need the coordinates of the irreducible q points calculated by the phonon code.

Best
Carla

[Gargee Bhattacharyya]

Thank You very much

[Gargee Bhattacharyya]

Sir ,
I have completed nscf calculation and used the grid generated from OUTCAR after optimized the structure. But I have used Cartesian . Is it okay ? The program has run successfully.