Dear Malgorzata, Thanks a lot for your comment. It works!!!
Right after editing phonon.f90 one has also to comment 173-174 lines in phq_readin.F90 before recompiling phonon. Regards Eyvaz. --- Malgorzata Wierzbowska <wierzbom at tcd.ie> wrote: > > Which version of the program and what > pseudopotentials do you use? > If this is ultrasoft pseudopotetial then do as > follows: > Edit the file phonon.F (or phonon.f90) in phlib (or > PH). > Go to the end and you see the place when > elph=.true.. > Write "call dvanqq" as it is below and recompile the > program. > > if (elph) then > call dvanqq > if (.not.trans) call elphon > call elphsum > endif > > If pseudo is normconserving and you have too big > el-ph couplings > (with good phonon spectra) probably it happens at > phonon vectors > which have small frequencies. > What exactly are the numbers? It would help to check > from which > region at frequency axis it comes. > Which q-points are particularly bad? > > Gosia > > > > ma Yanming wrote: > > > Dear Paolo, > > > > Thanks for your reply.I do choose q points using > Monkhorst-Pack K > > mesh. But I am still upset. I already increased > the K mesh to 48 48 48 > > when I calculated the EP coupling. To test the > performance in several > > high symmetry q if (elph) then points, I still got > the results for > > phonon linewidth far away from the experimental > data, despite I > > obtained the good results for phonon. :-( > > Any comments? > > > > Best Wishes! > > > > Yanming Ma > > > > > >> > I have been puzzled by the calculation of the > electron-phonon (EP) > >> > coupling coefficient lambda using PWSCF > >> > >> me too... > >> > >> The calculation of the electron-phonon coupling > coefficients > >> is presently done using a simple but not-so-smart > algorithm: > >> for each phonon q one calculates \lambda(q), > performing a > >> (slowly convergent) sum over k of electronic > states. > >> > >> > My question is how to choose the q points > properly in the first BZ? > >> > >> choose a uniform grid (Monkhorst-Pack, for > instance) and pick q-points > >> in the irreducible BZ. Unless your \lambda(q) is > strongly anisotropic > >> (this is the case of MgB_2, for instance: most of > the contribution to > >> \lambda comes from a specific phonon branch), the > convergence wrt > >> the q-grid shouldn't be a big problem. > >> > >> > So My question is what is the criterion for the > EP coupling > > > > convergency. > > > >> > >> it is more or less the same criterion that is > used to check for > >> convergence in metals: you should try > increasingly dense k-point > >> grids and a range of gaussian broadenings for > each grid. You should > >> find a range of gaussian broadening and of > k-point grids for which > >> the value of \lambda(q) is reasonably constant. > Unfortunately this > >> usually happens with rather large grids. > >> > >> There is some ongoing work on a better algorithm > for calculating > >> electron-phonon coupling coefficients using > tetrahedra. > >> > >> Paolo > >> -- > >> Paolo Giannozzi e-mail: giannozz at nest.sns.it > >> Scuola Normale Superiore Phone: +39/050509412 > >> Piazza dei Cavalieri 7 Fax: +39/050509417, > 050563513 > >> I-56126 Pisa, Italy Office: Lab. NEST, Via della > Faggiola 19 > >> > >> _______________________________________________ > >> Pw_forum mailing list > >> Pw_forum at pwscf.org > >> > http://www.democritos.it/mailman/listinfo/pw_forum > > > > > > > > > _________________________________________________________________ > > ?????????????????????????????? MSN Hotmail?? > http://www.hotmail.com > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum __________________________________________________ Do you Yahoo!? Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop! http://platinum.yahoo.com
