BSE on hybrid k mesh

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xiaoming_wang
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BSE on hybrid k mesh

#1 Post by xiaoming_wang » Tue Apr 06, 2021 1:09 am

Hello,

I'm trying to calculate BSE on a hybrid k mesh as in PRB 78, 085103 (2008), i.e., coarser at outer BZ but denser at inner BZ. However, I got error like

Code: Select all

 -----------------------------------------------------------------------------
|                     _     ____    _    _    _____     _                     |
|                    | |   |  _ \  | |  | |  / ____|   | |                    |
|                    | |   | |_) | | |  | | | |  __    | |                    |
|                    |_|   |  _ <  | |  | | | | |_ |   |_|                    |
|                     _    | |_) | | |__| | | |__| |    _                     |
|                    (_)   |____/   \____/   \_____|   (_)                    |
|                                                                             |
|     internal error in: mkpoints_full.F  at line: 1271                       |
|                                                                             |
|     internal error in KPOINT_IN_FULL_GRID: can not find 0 -0.25 0           |
|                                                                             |
 -----------------------------------------------------------------------------

and my KPOINT is

Code: Select all

Automatically generated mesh
       33
Reciprocal lattice
   -0.37500000000000    -0.37500000000000     0.00000000000000     0.06250000000000
   -0.37500000000000    -0.12500000000000     0.00000000000000     0.06250000000000
   -0.37500000000000     0.12500000000000     0.00000000000000     0.06250000000000
   -0.37500000000000     0.37500000000000     0.00000000000000     0.06250000000000
   -0.12500000000000    -0.37500000000000     0.00000000000000     0.06250000000000
   -0.12500000000000     0.37500000000000     0.00000000000000     0.06250000000000
    0.12500000000000    -0.37500000000000     0.00000000000000     0.06250000000000
    0.12500000000000     0.37500000000000     0.00000000000000     0.06250000000000
    0.37500000000000    -0.37500000000000     0.00000000000000     0.06250000000000
    0.37500000000000    -0.12500000000000     0.00000000000000     0.06250000000000
    0.37500000000000     0.12500000000000     0.00000000000000     0.06250000000000
    0.37500000000000     0.37500000000000     0.00000000000000     0.06250000000000
   -0.18750000000000    -0.18750000000000     0.00000000000000     0.01562500000000
   -0.18750000000000    -0.06250000000000     0.00000000000000     0.01562500000000
   -0.18750000000000     0.06250000000000     0.00000000000000     0.01562500000000
   -0.18750000000000     0.18750000000000     0.00000000000000     0.01562500000000
   -0.06250000000000    -0.18750000000000     0.00000000000000     0.01562500000000
   -0.06250000000000     0.18750000000000     0.00000000000000     0.01562500000000
    0.06250000000000    -0.18750000000000     0.00000000000000     0.01562500000000
    0.06250000000000     0.18750000000000     0.00000000000000     0.01562500000000
    0.18750000000000    -0.18750000000000     0.00000000000000     0.01562500000000
    0.18750000000000    -0.06250000000000     0.00000000000000     0.01562500000000
    0.18750000000000     0.06250000000000     0.00000000000000     0.01562500000000
    0.18750000000000     0.18750000000000     0.00000000000000     0.01562500000000
   -0.08333333333333    -0.08333333333333     0.00000000000000     0.00694444444444
   -0.08333333333333     0.00000000000000     0.00000000000000     0.00694444444444
   -0.08333333333333     0.08333333333333     0.00000000000000     0.00694444444444
    0.00000000000000    -0.08333333333333     0.00000000000000     0.00694444444444
    0.00000000000000     0.00000000000000     0.00000000000000     0.00694444444444
    0.00000000000000     0.08333333333333     0.00000000000000     0.00694444444444
    0.08333333333333    -0.08333333333333     0.00000000000000     0.00694444444444
    0.08333333333333     0.00000000000000     0.00000000000000     0.00694444444444
    0.08333333333333     0.08333333333333     0.00000000000000     0.00694444444444
The DFT part is fine but the (model)BSE part doesn't work. Any remedy?

Best,
Xiaoming

ferenc_karsai
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Re: BSE on hybrid k mesh

#2 Post by ferenc_karsai » Tue Apr 06, 2021 8:36 am

Have you tried the tutorial on model BSE's first?
Here it is:
https://www.vasp.at/wiki/index.php/Impr ... c_function

xiaoming_wang
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Re: BSE on hybrid k mesh

#3 Post by xiaoming_wang » Tue Apr 06, 2021 12:38 pm

Yes, I'm using the model BSE. I also want to use the hybrid k mesh to accelerate the convergence.

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Re: BSE on hybrid k mesh

#4 Post by ferenc_karsai » Tue Apr 06, 2021 2:33 pm

Can you please upload your calculations according to the forum guidelines?

xiaoming_wang
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Re: BSE on hybrid k mesh

#5 Post by xiaoming_wang » Tue Apr 06, 2021 3:46 pm

Thanks. I uploaded a small example to show the bug.
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Re: BSE on hybrid k mesh

#6 Post by xiaoming_wang » Wed Apr 07, 2021 5:31 am

The previous attachment has some problem. I attached a new one here.
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ferenc_karsai
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Re: BSE on hybrid k mesh

#7 Post by ferenc_karsai » Mon Apr 12, 2021 10:42 am

Unfortunately non-uniform k-meshes are not supported in the BSE routines in VASP.

If you have a look at the tutorials:
wiki/index.php/Improving_the_dielectric_function

There the dielectric function at different k-meshes with shifted origins were calculated.
This gives also a huge improvement and is potentially equally (or better) performing.

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Re: BSE on hybrid k mesh

#8 Post by xiaoming_wang » Mon Apr 12, 2021 1:04 pm

Thanks. It's good to know that. Btw, in the bse.F file there are many places where the function KPOINT_IN_FULL_GRID is called. If all the calculations (DFT and model BSE) are performed with ISYM=-1, do I really still need that function?

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Re: BSE on hybrid k mesh

#9 Post by ferenc_karsai » Thu Apr 15, 2021 6:05 am

You definitely need the full Brillouin zone to make the kk' pairs for the BSE Hamiltonian.

xiaoming_wang
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Re: BSE on hybrid k mesh

#10 Post by xiaoming_wang » Thu Apr 15, 2021 6:31 am

Thanks. I finally turn to UNIFORM shifted grid. However, I encountered similar bug even for the UNIFORM grid. Please see the attached files.
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ferenc_karsai
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Re: BSE on hybrid k mesh

#11 Post by ferenc_karsai » Tue Apr 27, 2021 8:18 am

Don't use the command KPOINT_BSE in your INCAR file, then it should work.

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