[QE-users] Regarding "occupations" keyword in input file

[Matteo Cococcioni]

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 <iurii.timrov at epfl.ch>
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 <users-bounces at lists.quantum-espresso.org> on behalf of
> Mohad Abbasnejad <mohaddeseh.abbasnejad at gmail.com>
> *Sent:* Thursday, August 13, 2020 7:58:21 PM
> *To:* users at lists.quantum-espresso.org
> *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:     mohaddeseh.abbasnejad at gmail.com
> Website:  academicstaff.uk.ac.ir/moabbasnejad
> ---------------------------------------------------------
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
> 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 matteo.cococcioni at unipv.it <lucio.andreani at unipv.it>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20200814/ae1afa7a/attachment.html>