Maxim, I believe Chun has a point here, and I beg to differ from what you say.
For some materials, it is important to include special k-points, so as to get a correct band structure and (eventually) forces - the most "famous" case would perhaps be graphene, with its K point. Even if your material hasn't such special characteristics, making the k-point mesh denser means that you are sampling the BZ more accurately and thus changing the part of the total energy that corresponds to the electronic band occupations. Just think of a simple numerical integration in 1-D. To say that you have a problem with an increasing k-point mesh density is a bit precipitated, unless you are sure that you have a very converged k-mesh. Chun's e-mail is actually very sensible: you should first relax your structure, and then increase the k-mesh to see its effects on the forces.Not only that, you should also check its effects on the band structure, although in principle this effect should be negligible, if you have performed a convergence study. Marcos On Sat, Oct 22, 2011 at 6:34 AM, Maxim Peskov <[email protected]> wrote: > Thanks for the comment, Chun. However, you have missed the point. > I guess it will be better if I rephrase my question: how can one restart > from scf-preconverged density matrix and increased kpoint set? With the > options I used such a restart would mean the forces are going crazy which > clearly indicate a problem. Even more, if I change kpoints it is better to > start from scratch than to use DM. Any ideas? > > --Max > > > 20 октября 2011, 20:04 от [email protected]: > > Hi, > > > > From the first ourput file, I found the following lines: > > > > outcoor: Final (unrelaxed) atomic coordinates (fractional): > > -0.00005348 0.49985936 0.49676159 1 1 C > > ... > > ... > > > > which means your first run is not converged. > > > > Best, > > > > Chun > > >
