Dear Paolo, Thanks for correction.
Bests, Eyvaz. --- 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 > (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. > > the exact meaning of the error is that the code > (PW/ewald.f90) > could not determine a value for alpha giving a > converged > G-space sum for the available set of G-vectors. > "Optimal" > is somewhat misleading in this respect. The only > reasons > for such error I can think of, iare either a very > weird structure, > or an exceedingly low cutoff > > Paolo > > -- > Paolo Giannozzi e-mail: > giannozz at nest.sns.it > Scuola Normale Superiore Phone: +39/050-509876, > Fax:-563513 > Piazza dei Cavalieri 7 I-56126 Pisa, Italy > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > Yahoo! Mail Stay connected, organized, and protected. Take the tour: http://tour.mail.yahoo.com/mailtour.html
