[Pw_forum] optimal alpha not found
eyvaz_isaev at yahoo.com
Mon May 9 18:30:41 CEST 2005
Thanks for correction.
--- Paolo Giannozzi <giannozz at nest.sns.it> wrote:
> On Thursday 05 May 2005 17:43, Eyvaz Isaev wrote:
> > Actually, the error means that the Ewald sum
> > energy contribution) could not converge for some
> > reason. I have to remind that the Ewald sum
> > of two parts: erf(\alpha R)/R and erfc(\alpha
> > 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
> > convergence for both G-, and R- sums.
> the exact meaning of the error is that the code
> could not determine a value for alpha giving a
> G-space sum for the available set of G-vectors.
> is somewhat misleading in this respect. The only
> for such error I can think of, iare either a very
> weird structure,
> or an exceedingly low cutoff
> Paolo Giannozzi e-mail:
> giannozz at nest.sns.it
> Scuola Normale Superiore Phone: +39/050-509876,
> Piazza dei Cavalieri 7 I-56126 Pisa, Italy
> Pw_forum mailing list
> Pw_forum at pwscf.org
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