Dear Lorenzo Sponza > calculation of a gapped system (occupations = 'fixed'). If I include > a large number of empty bands, these are the energies in Gamma:
You should always include some empty bands to get reliable band energies for insulators and semiconductors. > -4.8200-4.3169-0.9586-0.5478-0.5196-0.4977-0.0537 0.0095 with > occupations 1.0000 1.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 So the band gap estimated at the gamma of your syste is Eg = 3.3583 eV. This Eg value does not solely guarantee that the system is in the insulating state. > Instead, if I include only one empty band the result is > -4.8200-4.3169-0.5477 with occupations 1.0000 1.0000 0.0000 It's > like in if the latter case I was missing the state at -0.9586 eV. In this case the band gap estimated at the gamma is Eg = 3.7692 eV. Is there no band-crossing over the BZ? Did you check the band structure by plotting the energies along some k-point path? What kind of k-points mesh are you using for the SCF calculation? > but I was intrigued by this unexpected behaviour and I would like to > understand what's happening. Looks me like a numerical error induced by inappropriate setting (one empty band inclusion and/or complicated band structure). 西館数芽 Kazume NISHIDATE Ph.D Department of Systems Innovation Engineering, Graduate School of Science and Engineering, Iwate University 4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN Phone:+81-19-621-6391 kazume.nishid...@gmail.com, nisid...@iwate-u.ac.jp https://sites.google.com/site/nisidatelab/ _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
