In addition to what Iurii says, if you use occupation="smearing" the phonon code will assume your system is metallic and will never compute the dielectric tensor and Born effective charge which you need, instead to get the LO-TO splittings at Gamma (non analytic part of the dynamical matrix).
Greetings, Matteo Il giorno gio 13 ago 2020 alle ore 20:11 Timrov Iurii <[email protected]> ha scritto: > Dear Mohaddeseh, > > > To perform linear response calculations (phonons, calculation of Hubbard > parameters, etc.) for magnetic insulators, I use the procedure described in > q-e/HP/examples/example02/README. > > > If you have a gapped system, you should not use smearing, because there > can be numerical issues (due to the division by zero, because the DOS at > the Fermi level can be very small using small smearing for insulators, see > Eq. (79) in Rev. Mod. Phys. 73, 515 (2001)). > > > Greetings, > > Iurii > > > -- > Dr. Iurii Timrov > Postdoctoral Researcher > STI - IMX - THEOS and NCCR - MARVEL > Swiss Federal Institute of Technology Lausanne (EPFL) > CH-1015 Lausanne, Switzerland > +41 21 69 34 881 > http://people.epfl.ch/265334 > ------------------------------ > *From:* users <[email protected]> on behalf of > Mohad Abbasnejad <[email protected]> > *Sent:* Thursday, August 13, 2020 7:58:21 PM > *To:* [email protected] > *Subject:* [QE-users] Regarding "occupations" keyword in input file > > Dear QE users, > > Hello > > I have a general question. > My structure is Mott hubbard and has a band gap of about 2 eV. It is also > antiferromagnetic in its ground state. > I can obtain antiferromagnetic state and the desired band gap with hubbard > parameters by both ways: > occupations: smearing > occupations: fixed > A) I am wondering whether these occupations can have effect on the phonon > frequencies? > B) When is it preferable to use occupation fixed in our calculations? > > Any help would be appreciated. > Thanks in advance. > > Regards, > Mohaddeseh > > -- > --------------------------------------------------------- > Mohaddeseh Abbasnejad, > Assistant Professor of Physics, > Faculty of Physics, > Shahid Bahonar University of Kerman, > Kerman, Iran > P.O. Box 76169-133 > Tel: +98 34 31322199 > Fax: +98 34 33257434 > Cellphone: +98 917 731 7514 > E-Mail: [email protected] > Website: academicstaff.uk.ac.ir/moabbasnejad > --------------------------------------------------------- > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users -- Matteo Cococcioni Department of Physics University of Pavia Via Bassi 6, I-27100 Pavia, Italy tel +39-0382-987485 e-mail [email protected] <[email protected]>
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