[CP2K:781] Re: Parameter choice for GAPW

[Janos...@googlemail.com]

Dear All,

For many systems with with hard electron density GAPW seems to be a very 
promising approach. On the other hand side,
I have heard and read about its instability (such in this old post from 
Teo). I would like to ask the developers if these past issues are 
considered solved by now 
or if it is still not routine to run GAPW.

Best regards,

Janos


On Tuesday, March 11, 2008 at 7:03:43 AM UTC+1, Teo wrote:
>
> Axel,
>
> just a warning:
> There's a "serious" bug in GAPW, that Manuel discovered 1 year ago  
> and I identified clearly a couple of months ago, when your system is  
> interacting with the periodic replica (i.e. more than 0 order cell  
> interactions). This of course depends on the cell size (usually must  
> be quite small to pop up this error) and the system type/size.
>
> Keep it in mind in case you should observe strange behaviors  
> (compared with larger simulation boxes) for small cells (though this  
> is not the usual kind of run I would say).
>
> Moreover, for all people willing to use GAPW: don't expect it to be  
> as easy as running GPW. If, for GPW, you need to keep a constant eye  
> on your numbers, for GAPW you may want to keep the alert status  
> continuously ON.
> The main problem is that the method is far from being numerically  
> stable and you may easily find systems where an ACCURATE tuning of he  
> whole set of the parameters mentioned by Marcella is mandatory in  
> order to get realistic numbers.
>
> Just keep it in mind..
> Ciao,
> Teo
>
> On 11 Mar 2008, at 02:38, Axel wrote:
>
> >
> >
> >
> > On Mar 10, 8:35 pm, Marcella Iannuzzi <marcella.ia... at psi.ch>
> > wrote:
> >> Hi Axel,
> >
> > hi marcella,
> >
> > thanks a _lot_ this is _very_ helpful.
> > i'll have to make a few extra checks on
> > some of the parameters i'm using, but it
> > looks that most of my "gut-feeling" guesses
> > based on my experience with USPPs were pretty
> > close. seems like GAPW has a few more knobs
> > that in USPPs are automatically determined. ;-)
> >
> > [...]
> >
> >> - if you use all electron and  OT, convergence is significantly
> >> improved by setting the preconditioner to FULL_ALL
> >
> > hehe. i found that one already. with the preconditioner that was
> > good for GPW the convergence was indeed really bad for GAPW.
> >
> >> I am available for further clarifications on the method and its
> >> implementation.
> >
> > thanks again. i'll have to keep my tests running and
> > see if they produce something meaningful. so far, so lucky.
> >
> > ciao,
> >    axel.
> >
> >>
> >> ciao
> >>   Marcella
> >>
> >
> > >
>
>
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