How different are your optimized structural parameters from those reported in the literature? Looking at your input file, I would suggest to test convergence with degauss, maybe 0.05 (Rydberg!) is too large. Also try shifted k-points meshes, they should give faster convergence.
HTH GS Il giorno 06/mag/2011, alle ore 11.20, Alexander G. Kvashnin ha scritto: > Dear PWSCF community > > In my study I got a problem which I can't solve by myself, > unfortunately. I hope you can give me some tips where I made a > mistake. I have to to investigate the energy difference between > graphite and diamond, but I can't get trusted result.First of all, I > used LDA PP (PZ), I tested it by subsequently increasing of energy > cutoff (from 30 Ry to 120 Ry) as well as increasing of k-points mesh > (4x4x1 for graphite, 4x4x4 for diamond; 6x6x2 for graphite, 6x6x6 for diamond; > 8x8x3 for graphite, 8x8x8 for diamond; 10x10x4 for graphite, 10x10x10 for > diamond). > I got the difference between energies of diamond and graphite and tried to > understand it > trend (please, see attached figure). As you can see from the figure > difference between energy diamond and graphite is almost zero so I > can't say with confidence what structure is more favorable. > This result different from other theoretical and experimental > studies, therefore it seems that I did something wrong... > > My result: ~ 0.001?0.001 eV/atom > > _______________________________________________ > > | Energy difference (eV/atom) | Method | Reference | > | 0.03 |Experiment | PRB29_6996 | > | 0.01 | LDA-PP | PRB29_6996 | > | 0.04 | LDA-PP | PRB54_14994| > > ----------------------------------------------------------------------------------- > > Input files for diamond and graphite are attached to the letter. > > > -- > Sincerely yours > Alexander G. Kvashnin > -------------------------------------------------------------------------------------------------------------------------------- > First year of master degree study > Moscow Institute of Physics and Technology http://mipt.ru/ > 141700, Institutsky lane 9, Dolgoprudny, Moscow Region, Russia > > Junior research scientist > Technological Institute for Superhard > and Novel Carbon Materials > http://www.ntcstm.troitsk.ru/ > 142190, Central'naya St. 7a, Troitsk, Moscow Region, Russia > ================================================================ > > <input_diamond.opt><input_graphite.opt><Energy_difference.GIF>_______________________________________________ > 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/20110511/b74aaf67/attachment.htm
