[CP2K-user] [CP2K:13012] AIMD of ACN doesn't converge after 100 ps

[Abdullah Bin Faheem]

Dear Thomas,

Thank you for suggestions. I will try them out

Regards,
Abdullah

On Tuesday, March 24, 2020 at 11:03:52 PM UTC+9, tkuehne wrote:
>
> Dear Abdullah Bin Faheem, 
>
> there is nothing wrong. What you are observing is not due to incomplete 
> equilibration, but 
> rather a consequence, of incomplete SCF convergence. Beside time-step 
> errors, which in 
> your case may be non-negligible due to a discretized time-step of 1.0 fs, 
>  the so-called 
> „conserved quantity“ is in a numerical calculation only conserved at 
> perfect SCF convergence. 
> Hence, reducing the integration time-step and more importantly tightening 
> the EPS_SCF 
> should lead to a better conservation of the conserved quantity. However, 
> in a numerical 
> calculation the latter will never be perfectly conserved and it is up to 
> you to decided what 
> level gives you the best efficiency / accuracy compromise. 
> I personally, would suggest 0.5-0.75fs for the time-step and 1e-7 - 1e-6 
> for EPS_SCF when 
> using OT. I have commented on the differences between TD and OT wrt to 
> EPS_SCF in an 
> earlier posting. 
>
> Cheers, 
> Thomas
>
> Am 24.03.2020 um 14:03 schrieb Abdullah Bin Faheem <abdu... at gmail.com 
> <javascript:>>:
>
> Hello everyone,
>
> I performed AIMD of 60 Acetonitrile molecules using cp2k 5.1.0. However, I 
> noticed that "Cons Qty" keeps increasing and does not converge even after 
> 100 ps. While on the other hand, the kinetic and potential energies reach 
> equilibrium within 2-3 ps. Does this mean my system has not converged? Or 
> is there something wrong with my input file?
>
> If so, any suggestions would be greatly appreciated for possible 
> improvement/fixes. 
>
> I have attached the input and the energy output files, where the initial 
> geometry for ACN was taking from classical MD.
>
> Thank you for your time
>
> Best Regards,
> Abdullah Bin Faheem
>
> <Energies.png>
>
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>
> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
> td... at mail.upb.de <javascript:>
> +49/(0)5251/60-5726
>
>
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