[QE-users] Why my Hubbard parameter is so much bigger than what I find in the litterature?
Lorenzo Paulatto
lorenzo.paulatto at cnrs.fr
Tue Feb 28 13:34:29 CET 2023
On 2/28/23 13:22, NAIMI SALMA wrote:
> Ah ok, I see.
>
> So for the moment I have to take it from the litterature if i`m using
> a material with a closed-shell.
>
I would recommend you fit (or at least check) on some physical
parameter, like the band gap. As the precise value of U depends on the
reference wavefunctions, which depend on the pseudopotential, literature
values are not transferable.
regards
>
>
> ------------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
>
> ------------------------------------------------------------------------
> *From:* Iurii TIMROV <iurii.timrov at epfl.ch>
> *Sent:* Tuesday, February 28, 2023 1:16 PM
> *To:* NAIMI SALMA <salma_naimi at um5.ac.ma>; Quantum ESPRESSO users
> Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
>
> > Do I have to use occupations='fixed' instead of smearing just to compute the Hubbard
> parameter, or in all the calculations that I perform on CuI ?
>
>
> In all calculations
>
>
> > So nowto compute the Hubbard parameter I have to run one scf calculation with
> occupations='fixed' then run hp.x , right?
>
>
> Yes, but the U value will still be too large. So what I wanted to say
> previously is that I would not try to compute U using the HP code. It
> is a limitation of linear-response theory to compute U for
> closed-shell systems. We have some ideas how to overcome this issue,
> but it requires more testing and implementation in HP.
>
>
> 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 <http://people.epfl.ch/265334>
> ------------------------------------------------------------------------
> *From:* NAIMI SALMA <salma_naimi at um5.ac.ma>
> *Sent:* Tuesday, February 28, 2023 1:12:36 PM
> *To:* Iurii TIMROV; Quantum ESPRESSO users Forum
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
> Ok thank you.
>
> My material is a p-type semiconductor. So nowto compute the Hubbard
> parameter I have to run one scf calculation with occupations='fixed'
> then run hp.x , right?
>
> Do I have to use occupations='fixed' instead of smearing just to
> compute the Hubbard parameter, or in all the calculations that I
> perform on CuI ?
>
>
> -------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
>
> ------------------------------------------------------------------------
> *From:* Iurii TIMROV <iurii.timrov at epfl.ch>
> *Sent:* Tuesday, February 28, 2023 1:03 PM
> *To:* NAIMI SALMA <salma_naimi at um5.ac.ma>; Quantum ESPRESSO users
> Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
>
> Ok, I see. That message was meant for magnetic insulators and now I
> understand why it was confusing for you. We will modify it. Since your
> system is nonmagnetic and insulating, do not use smearing (instead use
> occupations='fixed').
>
>
> HTH
>
>
> 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 <http://people.epfl.ch/265334>
> ------------------------------------------------------------------------
> *From:* NAIMI SALMA <salma_naimi at um5.ac.ma>
> *Sent:* Tuesday, February 28, 2023 12:56:54 PM
> *To:* Iurii TIMROV; Quantum ESPRESSO users Forum
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
> Dear Iurii,
>
> Actually in the first attempt I had run just one scf calculation, but
> after running hp.x I got the following message in the output file:
>
> WARNING: The Fermi energy shift is zero or too big!
> This may happen in two cases:
> 1. The DOS at the Fermi level is too small:
> DOS(E_Fermi) = -0.3416E-35
> This means that most likely the system has a gap,
> and hence it should NOT be treated as a metal
> (otherwise numerical instabilities will appear).
> 2. Numerical instabilities due to too low cutoff
> for hard pseudopotentials.
>
> Stopping...
>
> Solution: Try to use the 2-step scf procedure as in HP/example02
>
>
> So based on that I followed HP/example02 then and ran the second scf
> calculation then hp.x
>
>
>
>
> -------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
>
>
> ------------------------------------------------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Iurii TIMROV via users <users at lists.quantum-espresso.org>
> *Sent:* Tuesday, February 28, 2023 12:44 PM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
>
> Dear Salma,
>
>
> There is no need to run two SCF calculations in your case (it is only
> needed for magnetic insulators, see README in example02 of HP).
>
>
> Cu is a problematic element for HP (linear response theory) because
> the 3d shell is full and in this case the approach is not suitable.
> For more details see J. Chem. Phys. 140, 121105 (2014).
>
>
> HTH
>
>
> 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 <http://people.epfl.ch/265334>
> ------------------------------------------------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> NAIMI SALMA <salma_naimi at um5.ac.ma>
> *Sent:* Tuesday, February 28, 2023 12:29:27 PM
> *To:* Quantum ESPRESSO users Forum
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
> Dear Giovanni,
>
> You`ll find attached the input files of scf1, scf2 and hp that I used
> to compute the hubbard parameter.
>
> Can you help me to know the exact error please!
>
>
>
>
> -------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
>
> ------------------------------------------------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Giovanni Cantele <giovanni.cantele at spin.cnr.it>
> *Sent:* Tuesday, February 28, 2023 12:18 PM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Why my Hubbard parameter is so much bigger
> than what I find in the litterature?
> Dear Salma,
>
> hard to say without knowing which material and atomic species you're
> dealing with. Generally speaking, if people expect a 5-6 eV U and you
> find more than 3 times more, I would suspect that an error is somwhere
> in the simulations.
> You should certainly check whether you used appropriate calculation
> parameters, e.g. BZ sampling, cutoff(s), and so on.
>
> Giovanni
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: https://sites.google.com/view/giovanni-cantele/home
>
>
> Il giorno mar 28 feb 2023 alle ore 12:04 NAIMI SALMA
> <salma_naimi at um5.ac.ma> ha scritto:
>
> Dear experts,
> I'm working on inorganic p-type semiconductor using qe-7.0 . I
> want to use GGA+U, so I computed the U value by following the
> steps from the HP directory/example 02 for NiO (scf1 then scf2
> then then hp) without including the magnetization because my
> material is not magnetic. My hubbard parameter was around 20 eV.
> While the used parameter for the same material in previous papers
> is around 5-6 eV ( Knowing that in previous papers they were
> extracting the U parameter from the litterature). The difference
> is big between their hubbard parameter and mine is that normal or
> did I do something wrong?
>
>
>
>
>
> -------------------------------------------------------
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
>
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> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing listusers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
--
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
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