[CP2K-user] [CP2K:13942] Large energy difference between md step and single point calculation

[Massimo Bocus]

Dear Haibei,

Thank you for your kind reply. I completely agree with you, however I think
that if reading the wavefunction makes the final output energy change by
200 kJ/mol with respect to a calculation "from scratch" then there must be
something conceptually wrong in how the code treats the two cases.
Moreover, it is completely impossible for me to save the wavefunction for
every step as the size of the file is about 30MB and I cannot know in
advance which steps I am going to take for the single point calculations.
If you have any other idea on how the problem could be solved, I would be
happy to know.

Best regards,
Massimo

On Tue, 22 Sep 2020 at 11:22, HB H <haibe... at gmail.com> wrote:

> *Hi  Massimo,*
>
> I think in MD simulations, the energy of one step is calculated not only
> based on the geometry, but also wavefunction of the last step. While the
> single point calculation only relies on the geometry.
>
> That being said, you should save the wfn files of each MD steps and use
> them as the restart wfn for single point calculations.(i.e. add "
> *WFN_RESTART_FILE_NAME* *XXXXX-RESTART.wfn*" in "DFT" section)
>
> Let know if I was wrong or not.
>
> Cheers,
> Haibei
>
>
> Massimo Bocus <massib... at gmail.com> 于2020年9月22日周二 下午4:55写道：
>
>> Dear CP2K users/developers,
>>
>> I am extracting some snapshots from an umbrella sampling simulation (with
>> PLUMED as dependency of CP2K 5.1) and I would like to recalculate their
>> energy at a higher level of theory. So to start I performed a single point
>> calculation at the same level of theory of the US simulation (PBE-D3) and,
>> surprisingly for me, I got very different results in the energy. In
>> particular, the energy of the MD step is:
>> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
>> -3520.987951048081868
>> While for the single point calculation:
>> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
>> -3520.903314334958850
>> Which is an enormous difference. Attached the two input scripts, the main
>> differences being the RUN_TIPE, the cell parameters (for the single point
>> they are just taken from the md output at the selected step) and the lack
>> of the MOTION section.
>> Does anybody have an idea on where this large energy difference could
>> come from?
>>
>> Thank you in advance,
>> Massimo Bocus
>>
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