Dear Dr. Lurii, Thank you so much for this great advice.
Regards Yuvam Bhateja On Mon, 17 Aug 2020, 2:09 pm Timrov Iurii, <[email protected]> wrote: > Dear Yuvam Bhateja, > > > > I am also simulating the same AFM Mott insulator. > > > For structural optimization I usually use occupation="smearing" and > smearing="Gaussian". > > Is it the correct way or should I choose different options. > > > That is fine. You can use also other smearing options, but in any case > since your system has a gap and you use the smearing then your system is > considered as a fake metal. So the type of smearing does not really matter > for magnetic insulators. For magnetic insulators, smearing is needed only > for technical reasons: in order to use starting_magnetization, the PW code > requires smearing. But once the calculation is converged, you can perform a > second SCF calculation with fixed occupations and by setting total > magnetization and starting from the previous converged SCF calculation > (reading wavefunctions and density/potential). After this second SCF, you > will have a magnetic insulator with no smearing. After this you can perform > various linear response calculations (PH, HP, etc.). > > > But for DOS you do not need to play this trick with two SCF calculations. > One SCF (the first one) is already enough. Then you can compute DOS using > the tetrahedron method or with the smearing if you want. > > > 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 > Yuvam Bhateja <[email protected]> > *Sent:* Friday, August 14, 2020 9:41:58 PM > *To:* Quantum ESPRESSO users Forum > *Subject:* Re: [QE-users] Regarding "occupations" keyword in input file > > Hello, > > I had the same question actually. > I am also simulating the same AFM Mott insulator. > For structural optimization I usually use occupation="smearing" and > smearing="Gaussian". > Is it the correct way or should I choose different options. > > And during DOS I use occupation="tetrahedra" with the relaxed calculation. > > Please guide me with this problem. > > Regards > Yuvam Bhateja > IIEST Shibpur > India > > On Fri, 14 Aug 2020, 3:49 pm Matteo Cococcioni, < > [email protected]> wrote: > >> 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]> >> _______________________________________________ >> 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 > > _______________________________________________ > 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
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