As discussed, many times in this forum, as well as in many textbooks, negative squared ferquencies are a signal of a mechanical instability. Are you sure that you want to spend a lot of computer resources calculating the supercondictive properties of an instable (and, hence, non-existent unless very special conditions occur) system? SB
--- swift text written and sent on the go On 13/ago/2009, at 11.00, Ali Tavana <anavat_ila at yahoo.com> wrote: > Dear QE users, > > I have a question about e-ph lambda, calculated by "matdyn" program. > I've found that for some frequencies the quantity "(alpha)^2*F(w)/w" > or "dos_a2F(w)/w" can be negative, most probably because of the > negative (imaginary) frequencies (I can't believe a2F(w) become > negative!). In "matdyn" program these negative values are considered > in lambda calculations. Should one remove these negative values as > these imaginary frequency modes can never exist in the system? then > where are those phonon branches? I think negative values of > frequency can show in some manner more strong electron structure > interaction, so what do you suggest one should do? > > regards, > Ali > > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum
