Dear Nicola, for smearing I used the default Gaussian one; The outliers seem to come from the tetrahedron method for a few "special" k-grids. I have to say I never observed this for any metal slabs I worked on so this seems to be a very particular case: a few isolated impurity bands (basically dispersion-free) inside an insulator band-gap.
Thanks for the information regarding mv and mp smearing that is certainly helpful! Best, Chris On Mon, Mar 25, 2019 at 1:46 AM Nicola Marzari <nicola.marz...@epfl.ch> wrote: > > > Is 8.2 (the outliar) given by the tetrahedron method? > > For insulators with a large band gap, if one uses mp or mv smearing, > there is the possibility that the code chooses a fermi energy just > below the top of the valence (with mv or mp) and just above the bottom > of the conduction (with mp), rather than in the middle of the gap > (albeit rare, this can happen, due to the fact that mv in these cases > can have two solutions for the fermi energy, and mp can have three). > > But your case seem to show a problem with the tetrahedron method, and > not sure that what is the problem. > > nicola > > > On 24/03/2019 04:21, Christoph Wolf wrote: > > Dear all, > > > > I am facing something rather interesting. My system is an insulator > > supercell with a metallic impurity. I tried to converge the Fermi energy > > wrt. to k-points and smearing in particular for "low temperatures" (~20 > > K). I observed the following behavior for a chosen number of k-points > > (e.g. 6 6 6 0 0 0): with smaller smearing the fermi level approaches the > > same value as the fermi level using the tetrahedron method (i.e. the > > tet_opt method represents 0 Ry smearing). > > > > however I found that for higher values for the k-point grid this does > > not seem to always work. For example for a 25 grid the value for the > > fermi level differs by ~0.8 eV! Is there a reason for this behavior? > > > > #k-grid kpnts Ef: smear tet > > 8 35 9.004 8.994 > > *25 455 8.974 8.201* > > 26 560 9.0068.996 > > > > Your help is very much appreciated! > > > > Best wishes, > > Chris > > -- > > Postdoctoral Researcher > > Center for Quantum Nanoscience, Institute for Basic Science > > Ewha Womans University, Seoul, South Korea > > > > _______________________________________________ > > users mailing list > > users@lists.quantum-espresso.org > > https://lists.quantum-espresso.org/mailman/listinfo/users > > > > > -- > ---------------------------------------------------------------------- > Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL > Director, National Centre for Competence in Research NCCR MARVEL, EPFL > http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project > -- Postdoctoral Researcher Center for Quantum Nanoscience, Institute for Basic Science Ewha Womans University, Seoul, South Korea
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