[CP2K-user] [CP2K:17138] Re: "Fastest" AIMD simulation settings/parameters

[Lenard Carroll]

It seems I am already using pretty much the best (fastest) settings
possible then.
For my AIMD simulations I do use Broyden Mixing, with a large-ish alpha
value, FULL_KINETIC predconditioner, ASPC extrapolation method, no UKS and
a 2 fs time step. I am, however, using CG for the minimizer instead of
DIIS. I am going to test that out and see how it looks.

Thank you very much Nick.

On Mon, Jun 13, 2022 at 12:48 AM Nicholas Winner <nwinner at berkeley.edu>
wrote:

> Here's a list of some things I can think of to increase speed. Probably
> not comprehensive. In the future include your input file for people so we
> can see what settings you are already trying.
>
> Will not compromise accuracy (test all options to find best)
>
>    1. Using traditional diagonalization:
>       1. Use broyden mixer, which is generally (not always!) faster.
>       2. In broyden use as large of a alpha value as you can afford while
>       still achieving convergence.
>    2. Using OT:
>       1. Change preconditioner to speed up the scf convergence. Normally
>       Full_all or Full_single_inverse are most effective, but full_kinetic might
>       be good if you have a huge system that takes too long to precondition.
>       2. if you know the system energy gap, you can supply a slight
>       underestimate of it to the OT preconditioner to help it converge faster
>       3. Change from CG (which is more robust) to DIIS which is usually
>       faster
>    3. Use ASPC wfn extrapolation
>    4. Inspect your SCF convergence. If you see unstable long convergence,
>    then increasing your precision settings might help you in the long run.
>
> Will/might compromise accuracy
>
>    1. Decrease EPS_DEFAULT
>    2. Decrease EPS_SCF (tolerance for scf convergence)
>    3. Use UKS = False. I.e. spin unpolarized if you not need it.
>    4. Use a larger MD time-step. Some systems are still okay with a large
>    time step of 2fs, could work for you.
>
> -Nick
> On Sunday, June 12, 2022 at 12:06:49 PM UTC-7 lenardc... at gmail.com wrote:
>
>> Just replying to this to bump it higher since I haven't received a
>> response yet.
>>
>> On Thursday, June 9, 2022 at 3:38:02 AM UTC+2 ASSIDUO Network wrote:
>>
>>> Hi there, I have been running AIMD simulations for about a year now and
>>> it originally started off really slow, only getting 60 fs per day. In
>>> particular, I used the NVT ensemble and the Nose-Hoover thermostat. When
>>> swapping to the Langevin ensemble and adaptive-Langevin thermostat, the
>>> simulation time improved to 200-600 fs a day.
>>>
>>> I wanted to know what settings/parameters you would suggest to improve
>>> the speed even further? That is, what are the best settings to choose to
>>> get the fastest performance?
>>>
>>> Key things to keep in mind for my work:
>>> Using GTH-PBE potential and the DZVP-MOLOPT-SR-GTH basis set. Fermi
>>> dirac smearing must also be used
>>>
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