[Wannier] Generating .mmn matrix for all pais of k-points

[Vahid Askarpour]

Dear Dominik,

I installed qe-6.1, which uses wannier90 version 2.1. I ran a self-consistent run followed by a non self-consistent run on the following k-points:

   0.0000000   0.0000000   0.0000000  0.0312500
   0.0000000   0.0000000   0.2500000  0.2500000
   0.0000000   0.0000000  -0.5000000  0.1250000
   0.0000000   0.2500000   0.2500000  0.1875000
   0.0000000   0.2500000  -0.5000000  0.7500000
   0.0000000   0.2500000  -0.2500000  0.3750000
   0.0000000  -0.5000000  -0.5000000  0.0937500
   0.2500000  -0.5000000  -0.2500000  0.1875000

Then I used the following si.sa.win file:

begin projections
 Si:sp3
end projections
num_bands 12
num_wann   8
iprint   2
dis_win_min -1000.000
dis_win_max    17.000
dis_froz_min -1000.000
dis_froz_max     6.500
num_iter     500
dis_num_iter 1000

nnkpts 8
begin nnkpts
1 1 0 0 0
1 2 0 0 0
1 3 0 0 0
1 4 0 0 0
1 5 0 0 0
1 6 0 0 0
1 7 0 0 0
1 8 0 0 0
end nnkpts

begin unit_cell_cart
bohr
-5.084373 0 5.084373
0 5.084373 5.084373
-5.084373 5.084373 0
end_unit_cell_cart

begin atoms_frac
Si       0.000000000   0.000000000   0.000000000
Si       0.250000000   0.250000000   0.250000000
end atoms_frac

begin kpoints
   0.0000000   0.0000000   0.0000000
   0.0000000   0.0000000   0.2500000
   0.0000000   0.0000000  -0.5000000
   0.0000000   0.2500000   0.2500000
   0.0000000   0.2500000  -0.5000000
   0.0000000   0.2500000  -0.2500000
   0.0000000  -0.5000000  -0.5000000
   0.2500000  -0.5000000  -0.2500000
end kpoints

Here I used the same k-points as before and asked for nearest neighbors for k-point=1

I ran wannier90.x -pp si.sa in parallel and get the following error:

Error: You must specify dimensions of the Monkhorst-Pack grid by setting mp_grid

How do you specify an mp_grid if the k-points are chosen randomly? Or am I missing something in the input?

Thanks,

Vahid


On Mar 16, 2017, at 8:46 PM, Vahid Askarpour <vh261281 at dal.ca<mailto:vh261281 at dal.ca>> wrote:

Dear Dominik,

Thank you so much for your quick response. I will follow your suggestions.

Best wishes,

Vahid

On Mar 16, 2017, at 8:35 PM, Dominik Gresch <greschd at phys.ethz.ch<mailto:greschd at phys.ethz.ch>> wrote:


Dear Vahid,

You can use the 'nnkpts' parameter (new in version 2.1) to explicitly specify for which k-point pairs the overlap should be calculated. This just side-steps the way that Wannier90 tries to calculate the nearest neighbours, and prints the neighbours you supply directly to the .nnkp file. To get the .mmn output for all pairs of k-points, you could generate the nnkpts block such that it includes all the overlaps you need.

For the interface to QE, you need to use the 'regular_mesh = .false.' when using pw2wannier90 to allow for non-regular k-grids to be used (new in QE v.6).

Best regards,

Dominik Gresch

On 17.03.2017 00:13, Vahid Askarpour wrote:
Dear Wannier Community,

I am attempting to include impurity scattering rate calculation in the EPW calculation. At present, EPW determines the scattering rates only due to electron-phonon scattering.

To include impurity scattering, one needs the overlap intergal for the lattice-periodic part of the wave function |u_nk> between any two k-points. The .mmn files creates such a file but it is only for the nearest neighbor k-points. Before attempting to redo a separate code, I have two questions:

1. Is it possible to output the .mmn file for all pairs of k-points?

2. Is it possible to do 1 not for a k-grid but for a list of random k-points? I suspect this can be done using


begin kpoints
# of k points
…
…
end kpoints

and the same k-points must be used in the preliminary self-consistent and non self-consistent calculations with QE.

I ask question 2 because for thermoelectric properties, one needs to select k-points with energies  ~0.5 eV above the CBM. So it is possible to generate a very dense k-grid (100^3) and only include the selected k-points in the impurity scattering rate calculation.

I would appreciate your help with the above questions.

Vahid

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



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