[Pw_forum] optimal alpha not found

Eyvaz Isaev eyvaz_isaev at yahoo.com
Thu May 5 19:43:33 CEST 2005

Hello Sergei,

May be something wrong with your structure?
Actually, the error means that the Ewald sum (ion-ion
energy contribution) could not converge for some
reason. I have to remind that the Ewald sum consists
of two parts: erf(\alpha R)/R and erfc(\alpha R)/R.
The first term has a fast convergence in G-space,
while  the second term converges in R-space. 
There are also 2 \alpha-dependent contributions,
excluded from sums.
Optimum \alpha has to be chosen so that it gives good
convergence for both G-, and R- sums.


--- Sergey Lisenkov <proffess at yandex.ru> wrote:
> Dear PWscf authors,
> I got the next message during pw.x run:
>      from ewald : error #         1
>      optimal alpha not found
> What is that? 
>  Sergey
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum

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