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Flat bands around E = 0 eV Date: 2020/09/27 05:23 Name: Malone Hi. I have another question, this time regarding band structure calculations. When I take a slab consisting of 20 atoms, for example, and conduct a calculation, in the end I get flat lines on a band diagram around 0 eV, where the program puts the chemical potential. At the other hand, if I count occupied bands by hand, the result is more acceptable. For example, I have 150 valence electrons in a spin-polarized calc, I have 150 occupied bands, so the LUMO will be 151st from the bottom. I extract energies for this 151st bands directly from the .Band file and it occurs to be around +60 eV, but bands do look like... bands, not just flat lines. I had encountered similar behaviour in quantum espresso, so this is not a complete surprise. Nevertheless, when I take a flat graphene sheet, I get the Dirac point exactly at 0 eV at K point. This is what confuses; maybe I do not understand completely what do the codes do when they place the E=0 mark. Could you describe what is going on here, please?

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Re: Flat bands around E = 0 eV ( No.1 ) Date: 2020/09/30 03:07 Name: Malone It is a bug in GNUPLOT's Autoscale. By default, bandgnu13 generates energy range from Emin to Emax, rather large values on the order of 100 eV. When you try to select a section of the plot with right click, it produces such "flat" bands as they appeared to be at the full scale from -200 to 200 eV. If one manually sets 'yra [-5, 5]', for example, the problem does not appear. Re: Flat bands around E = 0 eV ( No.2 ) Date: 2020/09/30 18:12 Name: Zsolt I also observed this behavior of gnuplot 5.2 (patchlevel 8.) -Zsolt

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