Excited state relaxation using ISMEAR=-2

[kousika_a]

Hi,

I am trying to excited state relaxation for my hexagonal boron nitride nanoribbons (armchair nanoribbons) using VASP 6.2.0 in GPUs. I am getting the following error after 2 ionic relaxations: | LAPACK: Routine ZPOTRF failed! INFO:39900 KPOINT:1 SPIN:1 .

I am attaching my input files and output files for your reference. Any inputs on how to get convergence would be helpful.

Thanks
Kousika

arm_hBN_VB.zip

[michael_wolloch]

Dear Kousika,

I tried to run your system on CPU first, and it did not give me any trouble (I stopped after 3 Ionic steps). However, I currently only have access to H100 Nvidia GPUs in a cluster with CUDA 13 and NVHPC 25.9, and I struggled to compile 6.2 with this brand new toolchain. I will get back to you after the weekend when I have tried this on GPUs with more information.

Thanks for your patience,

Michael

[kousika_a]

Hi Michael,

Thank you for your response. In some other cases (other defects), the delta SCF ends after 15-20 iterations. So, I want to understand whether this is because of the VASP version issue or GPU issue? Since in this article (https://arxiv.org/html/2505.04748v1#bib.bib9), they have mentioned that they could get convergence only with VASP 5.4.4 pathched version. Also, with CPUs, how many cores did you use to run the calculations?

Thank you
Kousika

[michael_wolloch]

Dear Kousika,

I have now tested your calculation using 6.2.0 and 2 GP100 GPUs (2 MPI ranks, 4 OpenMP threads) and could reproduce the error. However, my electronic system diverged before the LAPACK error occurred:

Code: Select all

CGA:  41    -0.112191488175E+04   -0.20661E-03   -0.19880E-03   400   0.392E-03 0.417E-04
CGA:  42    -0.112191502897E+04   -0.14721E-03   -0.14664E-03   400   0.462E-03 0.248E-04
CGA:  43    -0.112191500416E+04    0.24810E-04   -0.43515E-04   400   0.133E-02 0.276E-03
CGA:  44    -0.112191148631E+04    0.35178E-02   -0.21638E-04   400   0.526E-01 0.323E-02
CGA:  45    -0.112164858998E+04    0.26290E+00   -0.46295E-03   400   0.556E+01 0.273E+00
CGA:  46    -0.110299988488E+04    0.18649E+02   -0.12809E+00   400   0.287E+03 0.179E+02
CGA:  47    -0.100999629315E+04    0.93004E+02   -0.12321E+02   400   0.158E+04 0.320E+03
CGA:  48    -0.992294547525E+03    0.17702E+02   -0.12394E+03   400   0.129E+04 0.217E+03
CGA:  49    -0.904910510777E+03    0.87384E+02   -0.98481E+02   400   0.242E+04 0.428E+02
CGA:  50    -0.708645219421E+03    0.19627E+03   -0.15064E+03   400   0.498E+04-0.988E+03

Interestingly, when I reduce the plane-wave energy cutoff ENCUT from 600 to 500 eV, the calculation runs fine (I stopped it after 8 ionic steps). Note that 500 eV should be more than enough, since your highest ENMAX in the POTCAR is 400 eV, and you are not relaxing the cell.

I also tried to run with the original cutoff, but reduced the step width for the ionic relaxation via POTIM=0.3. In that case, the calculation also finished 10 steps without issues, with the last two only taking 10 and 11 SCF steps, respectively.

My initial CPU calculation was running on 128 cores.

We get reports that VASP 6 does not converge systems that used to converge with VASP 5 from time to time. Usually this cannot be confirmed, or VASP 5 converges to an unstable local minimum.

I think your calculation is a bit unstable, but I don't think that has anything to do with GPUs or the version of VASP used. Rather, the relaxation can push the electronic system a bit out of whack.

That this is reproducible, but clearly depends at least in part on Nr. of ranks, ENCUT, and POTIM, tells me that this is a very unstable system.

I would suggest making a few more tests to ensure more stability. You could also try to use selective dynamics to fix some ions in the nanoribbon to speed up convergence.

Let me know if there is something more you need help with, or if you have further questions.

Cheers, Michael