Actually, the standard of convergency for cut-off energy is not how much dE the system gained, but whether dE/dCut is near to 0 enough. Definitely, such a threahold, for dE/dCut, is also determined by yourself. The example from you was too extreme. Thinking about 100Ry as step, your result are too rough to hold the slope information. But when 10^(-5)Ry was using, even though it should give the very fine dE/dCut information as well, the results may be not good due to the accuracy of DFT, numerical methods, and computer limitation ( please consider the length of float and double float variable ). P.S.: Therefore, I think such question is not the one of sci. & tech. rather than your thinking method. This may be the reason that no person reply such a post in emuch.
-- GAO Zhe CMC Lab, Materials Science & Engineering Department, Seoul National University, South Korea At 2011-12-13 15:43:04,"??" <ptao10b at imr.ac.cn> wrote: >Dear all, > >I've asked sevral people about the convergence criteria of Ecutrho test. They >point out that the convergence will be achieved when the difference between >two adjacent scf calculation is smaller than 0.1 meV. However, they are not >very sure about the step length. From my view, the step length may pose huge >effects on our calculation. Consider the cases of step lengths are 100 Ry and >0.00001Ry respectively, the latter will be convergent immediately while the >former will not be so fast. > >For the resons above, I'm really confused now. And could any nice guy show me >the strict judgement of the convergence for Ecutrho? Thank you very much! > >Yours, >Plato Tao > >-- >------------------------------------------------------------------- >PH.D. candidate Peng Tao >Magnetism and Magnetic Materials Division >National Laboratory for Material Science >Institute of Metal Research, Chinese Academy of Sciences >Phone +86-024-83978751 >------------------------------------------------------------------- > > > > >_______________________________________________ >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/20111213/07d5406c/attachment.htm
