[QE-users] QE-7.1 and DFT+U

[Iurii TIMROV]

Dear Mahmoud,


> Explicitly, the starting_magnetization for O is removed in the new one. Does it mean the default value is still zero or the code searches for a better starting magnetization?


O atoms are nonmagnetic so that's why starting_magnetization for O was removed.


> But, comparing the results from qe-7.1 and qe-6.7, one notices significant changes in the input and outputs of feo_user_ns files.


FeO is metallic in DFT while it is insulting in nature. The difference between the new and old behaviour of QE is the starting occupations of the Fe-3d manifold. In older versions of QE (before 7.1) the starting occupations are hard-coded to be 6 (see PW/src/tabd.f90) while in QE7.1 the starting occupations are read from the pseudopotential (in this particular example it is 7). It turns out that in this example different starting occupations for Fe-3d states lead to the convergence to different metallic ground states of FeO, but in any case both are wrong ground states (one needs +U and to use starting_ns_eignevalue to open a gap and thus obtain the correct ground state). But if you want to restore the old behaviour of QE in the new version (i.e. 7.1) you need to specify in the input the new keyword Hubbard_occ(1,1) = 6.0 and Hubbard_occ(2,1) = 6.0 (because you have Fe1 and Fe2) - in this case the code reads the starting occupations from the input and not from the pseudopotential.


Greetings,

Iurii


--
Dr. Iurii TIMROV
Senior Research Scientist
Theory and Simulation of Materials (THEOS)
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 Mahmoud Payami Shabestari via users <users at lists.quantum-espresso.org>
Sent: Wednesday, June 29, 2022 1:16:53 PM
To: users at lists.quantum-espresso.org
Subject: [QE-users] QE-7.1 and DFT+U

Dear QE developers,

Hi.
In the new release QE-7.1, I investigated through the example08 of PW, the example of FeO.
In the release-notes, Incompatible changes, line 3, it is mentioned that "input syntax" is changed.
But, comparing the results from qe-7.1 and qe-6.7, one notices significant changes in the input and outputs of feo_user_ns files.
Explicitly, the starting_magnetization for O is removed in the new one. Does it mean the default value is still zero or the code searches for a better starting magnetization?
Any comments is highly appreciated.

With best regards,
Mahmoud Payami
NSTRI, AEOI, Tehran, Iran

Email: mpayami at aeoi.org.ir
Phone: +98 (0)21 82066504


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