Need help with making AIMD simulations faster!

[Akanksha]

Hi,

I am trying to run an AIMD simulation of an explicitly solvated system of ~280 atoms at 300 K and 1 bar pressure. However, I have noticed my simulation is very slow (Only reached about 200 fs in a day). I do have a few motion constraints on my solute molecules, which I believe could also make the simulations slower. 
Each MD step takes about 200 seconds to run with 6-10 SCF iterations. I am new to CP2K and AIMD in general, so I am not sure if this speed is normal. Could anyone please help me figure out if I am missing something or if there are any ways to make these simulations faster? Your help will be very much appreciated.

Here are the parameters I am using:
1) CP2K/2024.2 version (mpirun -np 32 -c 4 cp2k.psmp)
2) Anthracene and 2-bromophenol in a DMF box (17*14*14)
2) Calculation started from the last snapshot of a 5 ns classical MD run.
2) PBE-D3(BJ)/DZVP-MOLOPT/GTH 
3) ASPC(3) extrapolation
4) DIIS as the OT minimizer with FULL_SINGLE_INVERSE preconditioner

5) Timestep: 0.5 fs
5) CSVR thermostat with 50 fs time constant.

I have also attached the full input file and a plot of the constant-of-motion wrt time for your reference.

Please let me know if you need more information from me. I would really appreciate any feedback you can provide.

Thank you,

Akanksha

[Krack, Matthias]

Hi

 

At a first glance your setup looks fine to me. I don’t understand why it runs so slow. Maybe, you are overcommitting the available resources which often causes a significant slowdown. I suggest to use only one OMP thread per MPI rank. Running your input using an increasing number of CPU cores shows a reasonable scaling up to 64 CPU cores (cp2k v2025.2):

 

CPU cores (MPI ranks)	Average time per MD step [sec]
8	78
16	40
32	22
64	14
128	12

 

Best

 

Matthias

 

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