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Hi, I have got a learned potential of amorphous Pr-Fe. I then tried to do a prediction run with a large box (>17000 atoms). I first anealed the amorphous structure at 2000 K and then quenched it to 1200 K (I just copied CONTCAR to POSCAR and delete the velocity part before quenching). It runs well. But when I further annealed it at 1200 K there is a numerical error in the energy calculation:

POSCAR, INCAR and KPOINTS ok, starting setup
entering main loop
1 T= NaN E= NaN F= -.95135652E+05 E0= -.95135652E+05 EK= NaN SP= 0.00E+00 SK= 0.00E+00

Seems somewhere division by zero happens. I am not sure if it is a bug. Since it occurs at the first step, it is probably a problem of initialization. Could you give me some advise? I am not confident with the manual switch between annealing and quenching. btw, is there anyway to adapt the potential in other MD codes such as Lammps?

Thank you very much.

Hi, the NaN looks strange. Could you share a minimal reproducible please?

Ad Lammps interface) Not yet but we are working on it.

Cheers,
Marie-Therese

marie-therese.huebsch wrote: ↑Mon Sep 09, 2024 7:50 am

Hi, the NaN looks strange. Could you share a minimal reproducible please?

Ad Lammps interface) Not yet but we are working on it.

Cheers,
Marie-Therese

Hi, Marie-Therese,

Thank you for your reply. I just tried to skip the anealing and quenching from 2000K, but directly annealed the initial structure at 1200 K. I got the same error. The only difference between this run with the previous successful annealing run at 2000 K is that I set a very large NSW (see the attachment).

Puh, yes NSW = 4000000 is very large! I'd recommend splitting the calculation into multiple MD runs, like in example 6 in part 2 of the MD tutorial. Does this solve the issue?

So, this is strange. I just set a smaller NSW and NBLOCK as well (one zero less in the numbers). It goes well.

Ps: Please check out ML_OUTBLOCK instead of NBLOCK.

Could you try again if the combination of ML_OUTBLOCK = 20000, NSW=4000000 and ML_MODE = run works? And could you share an ML_FF file to reproduce the issue? (Doesn't have to be your best MLFF)

marie-therese.huebsch wrote: ↑Mon Sep 09, 2024 10:19 am

Could you try again if the combination of ML_OUTBLOCK = 20000, NSW=4000000 and ML_MODE = run works? And could you share an ML_FF file to reproduce the issue? (Doesn't have to be your best MLFF)

I just tried to set ML_OUTBLOCK = 20000, NSW=4000000. The std stops at "entering main loop" and the task is terminated then, don't know why (no error information in OUTCAR as well). My smallest ML_FF is 80MB which severely exceeds the size limit of attachments here.

Thanks for trying! Could you please share the ML_AB file? We can refit the ML_FF. The ML_FF are indeed quite large.

marie-therese.huebsch wrote: ↑Mon Sep 09, 2024 12:53 pm

Thanks for trying! Could you please share the ML_AB file? We can refit the ML_FF. The ML_FF are indeed quite large.

Thanks. I have attached the ML_AB. Please do a try.

Thank you! We could reproduce the problem.

Basically, the following must be ensured: ML_OUTBLOCK * NSW < 231-1.
So for now the only solution is to set a smaller NSW and split the MD runs. We will address this issue in a future release and add it to the known issues.

Does this clarify things for you?

PS: Don't forget to set ISYM=0 for MD in general.

marie-therese.huebsch wrote: ↑Tue Sep 10, 2024 12:00 pm

Thank you! We could reproduce the problem.

Basically, the following must be ensured: ML_OUTBLOCK * NSW < 2^31-1.
So for now the only solution is to set a smaller NSW and split the MD runs. We will address this issue in a future release and add it to the known issues.

Does this clarify things for you?

Thank you and yes it is clear for me.