[CP2K-user] [CP2K:17228] Best practices for large non periodic molecules

[Marco Severi]

Thank you very much for your comment. I saw in the documentation the 
constraint about the shape of the cell for the wavelet solver and was 
thinking about trying different solvers and cell shapes, now I am sure that 
it was not a bad idea. Thanks again!

Marco

Il giorno giovedì 23 giugno 2022 alle 16:24:20 UTC+2 mattwa... at gmail.com ha 
scritto:

> Quick note on the POISSON solver:
> The wavelet solver you have chosen is great because it only needs the 
> density to drop to zero at the box edges - so size of molecule + about 10A. 
> However, it only works for cubic cells so it needs to be largest molecule 
> dimension + 10A in all 3 directions. This could be inefficient for very 
> long or disc shaped molecules.
> Alternatively the MT or analytic solvers can be used but in each direction 
> they should be at least twice the minimum box size (I believe). This could 
> still be beneficial in some cases compared to above...
> Matt
>
> On Wednesday, 22 June 2022 at 16:01:28 UTC+1 marcos... at gmail.com wrote:
>
>> Thank you very much, I will try as soon as possible.
>>
>> Best,
>> Marco
>>
>> Il giorno mercoledì 22 giugno 2022 alle 16:45:14 UTC+2 hehn... at gmail.com 
>> ha scritto:
>>
>>> Dear Marco, 
>>>
>>> regarding convergence I would recommend to use the OUTER_SCF keyword and 
>>> SCF_GUESS RESTART, giving a relatively small number of inner SCF cycles, 
>>> maybe 20 to 50. Also choosing DIIS as minimizer can help to speed up 
>>> convergence.
>>>
>>> Best regards,
>>>
>>> Anna
>>>
>>> Am Mi., 22. Juni 2022 um 14:11 Uhr schrieb Marco Severi <
>>> marcos... at gmail.com>:
>>>
>>>> Good morning, 
>>>>
>>>> I am a fairly new CP2K user and I am trying to perform some 
>>>> calculations on a non-periodic molecular system of 657 atoms.  
>>>>
>>>> I am writing because I do not fully understand which keywords I should 
>>>> use and I have the feeling I am doing some rookie mistakes.
>>>>
>>>> At the moment I am trying to do some DFT calculations with the PBE 
>>>> functional and the dispersion correction. The molecule is about 35 Angstrom 
>>>> long and so I chose a 50x50x50 cell. The system is organometallic, contains 
>>>> 8 Fe atoms and the BF4- counterions. I tried to use the DZVP basis set but 
>>>> I quickly reached 100GB of occupied memory, is it normal? I am using the 
>>>> non "PERIODIC NONE" and "PSOLVER WAVELET" keywords  and the FULL_KINETIC 
>>>> preconditioner. I am using 5 grids with cutoff equal to 400 and rel_cutoff 
>>>> equal to 60. I tried to maintain all the other options as “default” as 
>>>> possible. I enclose the input and the output of the calculation. (I am 
>>>> aware that the attached example did not converge and that I can change the 
>>>> number of SCF iterations)
>>>>
>>>> I would like to know if those options are adequate for the type of 
>>>> calculation I am performing and if there is room for any improvement in the 
>>>> efficiency or in the convergence, since this calculation seems to converge 
>>>> particularly slowly. Any help or reference will be greatly appreciated. 
>>>>
>>>> Thanks in advance for your time and patience. 
>>>>
>>>> Kind regards, 
>>>>
>>>> Marco Severi 
>>>>
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>>>

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