[QE-users] Thermodynamics with DFT+U

[EDUARDO ARIEL MENENDEZ PROUPIN]

Iurii , Thanks again. I am trying with determine_num_pert_only = .true.
Running  pw.x I got the error
“Too many atoms. The dimensions of Hubbard_V must be increased”
en el archivo.

Browsing in the source files I see that I can solve it increasing the parameter natx in the file
/home/software/qe-6.8/Modules/parameters.f90
  INTEGER, PARAMETER :: natx = 50
Is that all I need? I have requested that to the cluster admin, as was unable to use the compilers, so I shall wait.



>> The atom indexes are relative to the atoms in the unit cell and include the
>> neighbor atoms in the eight surrounding unit cells.

>Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit
>cell inside of it. So in total there are 27 unit cells.


I should have written 26 instead of eight. I was thinking in 2D, Kirk would have beaten me like he did with Khan. 🙂

Best regards
Eduardo


Dear Eduardo,

> The atom indexes are relative to the atoms in the unit cell and include the
> neighbor atoms in the eight surrounding unit cells.

Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit
cell inside of it. So in total there are 27 unit cells.

> For defect calculations, I need to use a supercell with a different shape.
> How can I transfer the parameters to the supercell? I think this just needs a
> small code to generate
the parameter file for the supercell. I can do  it if this is not available. Is
it?

Yes, unfortunately the I and J couple indices will change if you change the
shape of the original real cell. The algorithm can be found in
PW/src/intersite_V.f90.

You can run the HP code by setting determine_num_pert_only = .true. For
DFT+U+V, it will only determine the indices of couples without running heavy
linear-response calculations. So then you can use this new file with the new
indices and add there the U and V values that you previously computed using a
smaller cell.


Eduardo A. Menéndez Proupin
Departamento de Física Aplicada I
Universidad de Sevilla
Teléfono: +34 9554 20231
https://personal.us.es/emenendez/
https://personal.us.es/emenendez/docencia/
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