On 08/18/2010 12:54 AM, meysam pazoki wrote: > > > ---------- Forwarded message ---------- > From: *meysam pazoki* <meysam.pazoki at gmail.com > <mailto:meysam.pazoki at gmail.com>> > Date: Tue, Jul 20, 2010 at 11:46 PM > Subject: Graphene Structural Relaxation > To: pw_forum-request at pwscf.org <mailto:pw_forum-request at pwscf.org> > > > Dear PWSCF users > I have a problem in relaxation of grahene super cell with 24 atoms. In > relaxation procedure ,graphene hooney-comb structure completely > destroys and atoms have no regular ordering after relaxation > procedure.I use pbe-rrkjus psudopotential,4 3 3 kpoint grid,30 rydberg > cutff energy,300 rydberg ecutrho. > I use both ion_damps & bfgs algorithms and get similar results. > If i change the ecutrho to 100, atoms have an irregular positions in 3 > dimension,but when ecut rho set to 300 atoms have irregular position > in-plane. > furthermore if i set > :trust_radius_ini=.1D0,trust_radius_max=.3D0,bfgs_ndim = 3, > I have the honeycomb structure but some of c atoms exprience great > forces like: > > atom 19 type 1 force = 11948.08469282 -219.69802882 0.00000000 > > atom 20 type 1 force = 11782.00343549 12.01959200 0.00000000 > > atom 21 type 1 force = 11748.09287051 115.25218004 0.00000000 > > atom 22 type 1 force = 11241.09464255 -222.56999757 0.00000000 > > atom 23 type 1 force = -0.50941109 0.26861287 0.00000000 > > atom 24 type 1 force = 11905.77649683 -91.34763119 0.00000000 >
These forces are simply crazy... I mean, if the units are those used by PWscf (Ry/Bohr) the forces that you are reporting are huge! If you have used the PP on the QE website, then the atomic positions and/or the cell dimensions that you have supplied to PWscf must be far off the equilibrium ones. Please provide an input file. GS > My question is what is wrong in my structure relaxation procedure that > result in such non-physical data. > > It would appreciated if anyone can help me in this problem > Thanks in advance > meysam pazoki > Ph.D student of physics > Sharif university of technology > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Gabriele Sclauzero, EPFL SB ITP CSEA PH H2 462, Station 3, CH-1015 Lausanne -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100818/ac7e79d7/attachment.htm
