Dear, Thank you for your explanation. I'll try both occupancies to see if the results of bandgap and DOS are very different. When I got the values, I can post the differences here.
I would like to ask if you could tell me why this question generates so different answers. As just like in the tutorials I saw, each one gave me a different answer. Best wishes, José Xavier Em terça-feira, 2 de novembro de 2021 00:41:19 BRT, Mahmoud Payami Shabestari <[email protected]> escreveu: Dear Xavier, > So, I can use the Fixed occupation and, if the energy levels show a small > bandgap, I introduce the >Smearing. Is it right? Yes, exactly. >If yes, I just have to add the nbnd function in the input file? Yes. It suffices to put nbnd equal to N/2 + 1 (N is number of electrons). Mahmoud > From: xavier neto via users <[email protected]> > > To: Mahmoud Payami Shabestari <[email protected]>, Quantum ESPRESSO users > Forum <[email protected]> > Date: Mon, 1 Nov 2021 21:04:31 -0300 > Subject: [QE-users] occupation in biological molecules and band gap > > Dear Mahmoud Payami, > > Thank you for your answer. It helps me a lot. > > So, I can use the Fixed occupation and, if the energy levels show a small > bandgap, I introduce the Smearing. Is it right? > > > > About the second question. I've read that the result of HOMO - LUMO, obtained > after the SCF calculation, can give the bandgap. Can I obtain the bandgap in > that way? If yes, I just have to add the nbnd function in the input file? > > On 11/1/21 02:04, Mahmoud Payami Shabestari wrote: > >> >> Dear José Xavier, >> >> Hi. >> >> Smearing for the occupations is used when the levels near HOMO are so close >> (commonly in metals near Fermi level) that in consecutive iterations they >> may exchange positions and lead to nonconvergence. For semiconductors with >> 3-5 eV gap I think it won't help. >> >> Bests >> >> >> Mahmoud Payami >> >> NSTRI, AEOI, Tehran, Iran >> >> >> >> >> >>> From: José Xavier via users <[email protected]> >>> To: "[email protected]" <[email protected]> >>> Date: Mon, 1 Nov 2021 00:18:55 +0000 (UTC) >>> Subject: [QE-users] occupation in biological molecules and band gap >>> >>> Dear all, >>> >>> I'm new in QE. The group that I'm working with usually calculates the >>> properties of biologically relevant molecules, like amino acids, hormones, >>> neurotransmitters, and drugs, and I would like to introduce the QE code to >>> the group. Their previous papers have shown that the bandgap of these >>> crystals is something between 3-5 eV, which I understand to be in the >>> semiconductor range. >>> >>> I've watched/read some tutorials about QE, and some of these showed that >>> the occupation of semiconductors should be "smearing", other ones that it >>> should be "fixed", but no one showed calculations with this kind of >>> molecules. What value should I use for the SCF and electronic calculations >>> of the crystals that I'm going to work on (amino acids, hormones, >>> neurotransmitters, and drugs)? >>> >>> *Are there any differences when the molecule has a metal, like the Heme >>> group? >>> >>> Besides, I would like to ask if there is a calculation that I could perform >>> to obtain the bandgap of these molecules. Is it only possible if I create >>> the band structure figure and calculate the difference between the peaks in >>> VB and CB? >>> >>> Thank you for your help, >>> >>> Sincerely, >>> José Xavier >>> >>> _______________________________________________ >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >>> users mailing list [email protected] >>> https://lists.quantum-espresso.org/mailman/listinfo/users >>> >> >> > _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
