Dear Max, One can see that \lambda you got is quite small, just around zero. So, a reason might be numerical noise for such a kind small \lambda. \gamma depends also on production of two delta functions which couples two electronic states at the Fermi Surface and it converges slowly. I suggest you should perform tests with respect to number of k-points (more fine that you used), and higher cutoff energies.
Bests, Eyvaz. P.S. Just today I have got \lambda for a metal, around 0.5, and everything went smoothly. --- ?? ???? <chen_shao_hua197 at yahoo.com.tw> wrote: > Dear Eyvaz and forum's members, > > When I calculated the el-ph coupling constant > \lambda > of material.I find some negative value > > Electron-phonon coupling constant, lambda > > Broadening 0.0100 lambda 0.0008 dos_el > 0.3719 > Broadening 0.0200 lambda 0.0012 dos_el > 0.3674 > Broadening 0.0300 lambda 0.0021 dos_el > 0.3565 > Broadening 0.0400 lambda -0.0098 dos_el > 0.3821 > Broadening 0.0500 lambda -0.0303 dos_el > 0.5231 > Broadening 0.0600 lambda -0.0394 dos_el > 0.7545 > Broadening 0.0700 lambda -0.0408 dos_el > 1.0409 > Broadening 0.0800 lambda -0.0382 dos_el > 1.3767 > Broadening 0.0900 lambda -0.0333 dos_el > 1.7603 > Broadening 0.1000 lambda -0.0274 dos_el > 2.1824 > > Also find some negative value in gam.line > e.g. > 24 0.0000 0.0000 0.0000 -0.0001 0.0000 > -0.0001 ***** 0.0000 0.0000 > > But no negative frequency found in matdyn.freq > > I thought -\lambda comes from -\gamma (phonon > linewidth), and -\gamma comes from -\omega > (frequency) by its definitions. > > So I wonder why I got -\lambda and -\gamma (It > should > be >=0) > even frequency \omega seems fine (no negative) ??? > > Should I just try check convergence of \gamma in > dependent on cutoff energy and k-points sampling ? > (from forum's "search archive", title " 3 questions > about elph file of Calculation of electron-phonon > interaction coefficients" suggestions ) > > Thanks in advance > > max > PHD candidate > Physics department, National Taiwan > University,Taiwan > > > > ____________________________________________________________________________________________ > 2G?i?H???h???HYahoo?_???q?l?H?c2.0???A???@???l?]???????I > http://tw.mg0.mail.yahoo.com/dc/landing > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > ------------------------------------------------------------------- Prof. Eyvaz Isaev, Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, IFM, Linkoping University, Sweden Condensed Matter Theory Group, Uppsala University, Sweden Eyvaz.Isaev at fysik.uu.se, eyvaz_isaev at yahoo.com ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs
