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

[Yuvam Bhateja]

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, <matteo.cococcioni at unipv.it>
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 <
> 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
>> ---------------------------------------------------------
>>
>> _______________________________________________
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>
>
>
> --
> 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>
> _______________________________________________
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