[CP2K:726] Re: recentering option for isolated system calculations

[Juerg Hutter]

Hi

the wavelet solver uses its own FFT routine. These
routines are the same as the FFTSG package in CP2K.
Yes, this is duplicating code, but it came pre-packed
by the developers of the wavelet solver.
The FFT library you choose in the input affects only
the FFTs in the regular CP2K code, not the wavelet solver.

best regards

Juerg

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich           E-mail: hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
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On Tue, 4 Mar 2008, Axel wrote:

>
>
>
> On Mar 4, 5:29 pm, Rad <rad.... at arl.army.mil> wrote:
>> Axel,
>>
>> I am struggling with a large isolated system and I am using the MT
>> poisson solver. Maybe I should try the wavelet based PS. Could you
>> please let me know how to set up the section and if there are any
>
> syntax and parameters is in the cp2k input reference manual.
>
> BTW: it would be nice to have an explanation for the requirement
> of FFTSG as preferred FFT, it seemed to work with FFTW3 as well and
> i would have expected the code to crash or refuse the run, if
> this was a "hard" requirement.
>
>> caveats? (Teo mentioned that and I forgot the syntax) Do we have to
>> have
>> a vaccum of 20% for the wavelet method or is it only for the MT
>> scheme?
>
> i would consider 20% vacuum (how do you compute it?) to be far too
> little for MT p-solver. you may get away with it if your system has
> favorable error cancellation, but i would not depend on it.
>
> formally, the MT p-solver requires a box of twice the size of a
> sphere that encloses the total charge density of your molecule
> (i.e. atoms _and_ electron density). i can see small errors crop
> up on my (weakly interacting) test system starting from exactly
> the %50 mark and then the errors became intolerably large at
> having 40% vacuum.
>
> cheers,
>    axel.
>
>>
>> Thanks
>> Rad
>>
>
> >
>