Hi, XCryDen gives you q-points coordinates with respect to basis vectors. But X(1,1,0) and K(3/4,3/4,0) are in Cartesian and in units of 2*\pi/a.
If I am not wrong, matdyn.x uses (at least, always I used) q-points in Cartesian, so, you have to transform these points to Cartesian. Or see a text book (H.Jones The Theory of Brillouin zones and electronic states in crystals, or J. Callaway Energy band Theory, or whatever you like) to find them in Cartesian. Bests, Eyvaz. ________________________________ From: lucking-pine <[email protected]> To: PWSCF Forum <pw_forum at pwscf.org> Sent: Wed, May 11, 2011 5:34:10 AM Subject: Re: [Pw_forum] why K-X point of phonon dispersion is wrong? Dear Eyvaz Isaev: Thank you for your advice.My k-point is chosen by Xcrysden.such as: G 0.0000000000 0.0000000000 0.0000000000 K -0.7500000000 -0.3750000000 -0.3750000000 X -0.5000000000 0.0000000000 -0.5000000000 G 0.0000000000 0.0000000000 0.0000000000 L - 0.5000000000 -0.5000000000 -0.5000000000 X 0.0000000000 -0.5000000000 -0.5000000000 W -0.2500000000 -0.5000000000 -0.7500000000 L -0.5000000000 -0.5000000000 -0.5000000000 and I try to use your advice through using 3 type of attempt. 1.only chang K,Xpoint of K-G path to K(0.75,0.75,0), X point (1, 1, 0) 2.all k point multipy 2 times. such as: G 0.0000000000 0.0000000000 0.0000000000 K -1.5000000000 -0.7500000000 -0.7500000000 X -1.0000000000 0.0000000000 -1.0000000000 G 0.0000000000 0.0000000000 0.0000000000 L - 1.0000000000 -1.0000000000 -1.0000000000 X 0.0000000000 -1.0000000000 -1.0000000000 W -0.5000000000 -1.0000000000 -1.5000000000 L -1.0000000000 -1.0000000000 -1.0000000000 3.only K,Xpoint of K-G path multiply 2 times. such as G 0.0000000000 0.0000000000 0.0000000000 K -1.5000000000 -0.7500000000 -0.7500000000 X -1.0000000000 0.0000000000 -1.0000000000 G 0.0000000000 0.0000000000 0.0000000000 L - 0.5000000000 -0.5000000000 -0.5000000000 X 0.0000000000 -0.5000000000 -0.5000000000 W -0.2500000000 -0.5000000000 -0.7500000000 L -0.5000000000 -0.5000000000 -0.5000000000 However,all this attempts yield wrong picture. So,this must be something I didn't understand correctly.Would you tell me where is my fault ? 2011/5/6 Eyvaz Isaev <eyvaz_isaev at yahoo.com> Hi, > >First of all I would recommend the use of PlotPhon utility to plot phonon >dispersion relations. For this one you have to have calculated interatomic >force >constants matrix (*.fc) file. > >Regarding your particular question: you should choose K(0.75,0.75,0), then >from >the K point go to the X point (1, 1, 0) which is equivalent to > >the X(1,0,0) point. Then from the X(1,0,0) to the Gamma (0,0,0) point. >Dashed line just means that we can continue in this direction to match phonons >at the X point (i.e. it is an intermediate point from the Gamma to the X >point) >. > >Please also provide your affiliation. > >Bests, >Eyvaz > > >------------------------------------------------------------------- >Prof. Eyvaz Isaev, >Department of Physics, Chemistry, and Biology (IFM), Linkoping University, >Sweden > >Theoretical Physics Department, Moscow State Institute of Steel & Alloys, >Russia, > >isaev at ifm.liu.se, eyvaz_isaev at yahoo.com > > > > > ________________________________ From: lucking-pine <songsong19840614 at gmail.com> >To: Pw_forum at pwscf.org >Sent: Fri, May 6, 2011 2:50:16 PM >Subject: [Pw_forum] why K-X point of phonon dispersion is wrong? > > > >My pwscf is used in calculating Si phonon dispersion.The trend of picture in >most special Symmetry is right.But the only K-X is wrong.I use Xcrysden to >get K-point. >I found most paper is dash line in 'K' point.So what is mean? Please anyone >could tell me! Thanks! >The attachment is my picture and reference paper. >_______________________________________________ >Pw_forum mailing list >Pw_forum at pwscf.org >http://www.democritos.it/mailman/listinfo/pw_forum > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110513/418e656a/attachment-0001.htm
