Not sure what is happening and why: the tetrahedron method works well for "true" metals, maybe it doesn't work well for a case like yours. Look at one-electron energies in the two cases and in particular to the position of the impurity level (if easy to localize) and to its occupancy: is there any other obvious anomaly?
Paolo Paolo On Sun, Mar 24, 2019 at 9:21 AM Christoph Wolf <wolf.christoph@qns.science> 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 9.006 8.996 > > 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 -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
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