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

[Timrov Iurii]

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


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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
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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

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Mohaddeseh Abbasnejad,
Assistant Professor of Physics,
Faculty of Physics,
Shahid Bahonar University of Kerman,
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