[QE-users] Problems with hp.x
Timrov Iurii
iurii.timrov at epfl.ch
Thu Jun 18 10:12:10 CEST 2020
> ...because the 2 shell is fully occupied
because the d shell is fully occupied.
Sorry!
Iurii
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Timrov Iurii <iurii.timrov at epfl.ch>
Sent: Thursday, June 18, 2020 10:08:19 AM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] Problems with hp.x
> Since it's Cu(I) isn't
> that a closed shell, a d10 system aswell? I was wondering why the
> linear-response theory works in this case but not for Zn2+.
Indeed, Cu2O has the same problem as ZnO, because the 2 shell is fully occupied. In our paper, for Cu2O we obtained U for Cu-3d states of 11.3 eV - this is from a one-shot calculation. This value of U is already large. If U is computed in a self-consistent way, then at 2nd, 3rd, and next iterations U for Cu-3d states will be larger and larger. This is because the d shell is full and it is pushed deeper and deeper in energy with increasing U, and the linear-response theory gives larger and larger values of U at the subsequent iterations. I realized quite late that Cu2O is not really a good "demonstrator" for our PRB 2018 paper - however, on the other hand, still it is OK just for the sake of benchmarking DFPT versus the finite-difference supercell approach of PRB 71, 035105 (2005).
Concerning the question why in the one-shot calculation Cu-3d (in Cu2O) has U of ~11 eV and Zn-3d (in ZnO) has U of ~20 eV, is because Zn-3d states are deeper in energy than Cu-3d states (at the DFT level - which is typically the starting point for the HP calculation).
HTH
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 dv009200 at fh-muenster.de <dv009200 at fh-muenster.de>
Sent: Wednesday, June 17, 2020 11:42:28 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] Problems with hp.x
Thanks again thats for sure very helpful.
Just out of curiosity I may have one more question: In the paper thats the
basis of the hp.x code (I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B
98, 085127, DOI:10.1103/PhysRevB.98.085127) the Hubbard U parameter of
Cu2O is computed by the linear-response theory. Since it's Cu(I) isn't
that a closed shell, a d10 system aswell? I was wondering why the
linear-response theory works in this case but not for Zn2+.
Best regards
Dominik Voigt
Dominik Voigt
PhD Student University of Applied Sciences Münster
Department of Physical Chemistry
>
> Dear Dominik
>
>> the method you suggested Giuseppe. I don't quite know whats the 'right'
>> distance between the valence band and the d-band? Can I use experimental
>> data from xps/ups spectra for that matter or do you have other
>> suggestions?
>
> Yes, it is actually what I did with ZnO. As I remarked in my previous
> message, it is going to work well if you apply the correction also to
> the S 3p shell, in a DFT+U(Zn,S) fashion. In wurtzite ZnO the strong
> curvature of the Zn 4s conduction band is such that the CB is
> substantially free from delocalization error and it is a good absolute
> reference. If you know the position of the Fermi level (which can
> depend on intrinsic defects in real samples) with respect to the CB,
> then you can reasonably estimate the position of the Zn 3d band.
> I hope I've not added entropy...
> Best
> Giuseppe
>
> Quoting dv009200 at fh-muenster.de:
>
>> Thanks all for the helpful comments and interesting papers. I'm fine
>> correcting the delocalization error of the Zn 3d states 'semiempirical'
>> by
>> the method you suggested Giuseppe. I don't quite know whats the 'right'
>> distance between the valence band and the d-band? Can I use experimental
>> data from xps/ups spectra for that matter or do you have other
>> suggestions?
>>
>> Best regards
>>
>> Dominik Voigt
>>
>> Dominik Voigt
>> PhD Student University of Applied Sciences Münster
>> Department of Physical Chemistry
>>
>>
>>
>>> Dear All,
>>>
>>>
>>> Giuseppe is right, this is a limitation of the current implementation
>>> of
>>> the linear-response theory to compute Hubbard parameters for
>>> closed-shell
>>> systems (like ZnO, ZnS, etc.). This "limitation" is known, and there is
>>> some comment about this in q-e/HP/Doc/README. Please check this paper
>>> for
>>> more details:
>>> <https://aip.scitation.org/doi/10.1063/1.4869718>
>>>
>>> https://aip.scitation.org/doi/10.1063/1.4869718
>>>
>>>
>>> The developers of the HP code are planning to investigate this issue in
>>> more detail, and hopefully we will come out with some solution in the
>>> near
>>> future.
>>>
>>>
>>> Best regards,
>>>
>>> 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
>>> Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it>
>>> Sent: Monday, June 15, 2020 10:55:59 PM
>>> To: Quantum ESPRESSO users Forum
>>> Subject: Re: [QE-users] Problems with hp.x
>>>
>>>
>>> Dear Dominik
>>> I suppose that the problem is not in hp.x, but in the application of
>>> the linear-response method itself to Zn(2+). Zn(2+) is a d10
>>> transition metal, with the 3d band fully occupied. In ZnO, e.g., the
>>> Zn 3d band is quite narrow and placed below the O 2p valence band, and
>>> I suppose that the same holds for ZnS, with the Zn 3d band pushing up
>>> the S 3p band. When you apply the LR method to Zn, you compute
>>> quantities such as d(alpha)/dn, where alpha is the (small)
>>> perturbation and n is the occupation number of d orbitals on site I
>>> (see International Journal of Quantum Chemistry 2014, 114, 14 for
>>> details). If the shell is full, then you can perturb whatever you want
>>> but you will never obtain more than the full occupation of the shell
>>> that you already have in the unperturbed system. This is likely the
>>> reason for the crazy values of LR U you obtain. If you want to correct
>>> the strong delocalization error of the Zn 3d narrow band within the
>>> DFT+U formalism, then you must use a "semiempirical" approach,
>>> choosing, e.g., the U value that places the Zn 3d shell at the correct
>>> distance from the valence band maximum. In this case, I would
>>> recommend the use of a second +U correction on the S 3p shell, which
>>> should ensure a good recovery of the ZnS band gap. I've satisfactorily
>>> used this scheme in the case of ZnO in several publications, from
>>> which you may want to take inspiration (Adv. Energy Mater. 2014, 4,
>>> 1301694).
>>> HTH
>>> Giuseppe
>>>
>>> Quoting dv009200 at fh-muenster.de:
>>>
>>>> Hello everyone,
>>>>
>>>> I'm trying to calculate the hubbard u parameter for Zn in Zinc sulfide
>>>> (sphalerite structure) with the help of the hp.x code. The
>>>> calculations
>>>> terminate normally without any errors. The problem is that I get
>>>> (presumably) way too high values for U that also won't converge (if I
>>>> take
>>>> the value I got from a one-shot calculation and plug it in the SCF
>>>> input
>>>> and then redo the HP calculation).
>>>>
>>>> For example in the first step I calculate a U = 75.7035 in the second
>>>> iteration I get U = 804.2405 and in the third U = 30999.2684.
>>>>
>>>> This seems unreasonable considering that the calculations for the
>>>> provided
>>>> examples in the 'HP' folder work fine and converge fast without such a
>>>> massive change to a certain value for U using the above described
>>>> scheme.
>>>>
>>>> Has someone an idea what is causing this trouble in my system? I
>>>> already
>>>> tried different PPs, functionals, U_projection_type, thresholds and k
>>>> and
>>>> q point grids all without success.
>>>>
>>>> Below is my input for the scf and hp calculation
>>>>
>>>> SCF-input:
>>>> &control
>>>> calculation='scf'
>>>> restart_mode='from_scratch',
>>>> pseudo_dir = '/home/dominik/codes/QE6.5/pseudo/'
>>>> outdir='/home/dominik/codes/QE6.5/tempdir/'
>>>> prefix='zns'
>>>> /
>>>> &SYSTEM
>>>> ibrav = 2
>>>> celldm(1)=10.291937439
>>>> nat = 2
>>>> ntyp = 2
>>>> ecutwfc = 60.0
>>>> ecutrho= 720.0
>>>> lda_plus_u = .true.
>>>> lda_plus_u_kind = 0
>>>> U_projection_type = 'atomic'
>>>> Hubbard_U(1) = 1d-8
>>>> /
>>>> &electrons
>>>> mixing_beta=0.7
>>>> conv_thr=1d-15
>>>> /
>>>> ATOMIC_SPECIES
>>>> Zn 65.39 Zn.pbe-dn-rrkjus_psl.0.2.2.UPF
>>>> S 32.07 S.pbe-n-rrkjus_psl.0.1.UPF
>>>> ATOMIC_POSITIONS {alat}
>>>> Zn 0.000000 0.000000 0.000000
>>>> S 0.250000 0.250000 0.250000
>>>> K_POINTS automatic
>>>> 12 12 12 0 0 0
>>>>
>>>>
>>>> HP-input:
>>>> &inputhp
>>>> prefix='zns'
>>>> outdir='/home/dominik/codes/QE6.5/tempdir/'
>>>> nq1 = 2
>>>> nq2 = 2
>>>> nq3 = 2
>>>> conv_thr_chi = 1.0d-10
>>>> iverbosity =2
>>>> /
>>>>
>>>>
>>>> Best regards
>>>>
>>>>
>>>> Dominik Voigt
>>>>
>>>> Dominik Voigt
>>>> PhD Student University of Applied Sciences Münster
>>>> Department of Physical Chemistry
>>>>
>>>> _______________________________________________
>>>> Quantum ESPRESSO is supported by MaX
>>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>>> users mailing list users at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>
>>>
>>>
>>> GIUSEPPE MATTIOLI
>>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
>>> Via Salaria Km 29,300 - C.P. 10
>>> I-00015 - Monterotondo Scalo (RM)
>>> Mob (*preferred*) +39 373 7305625
>>> Tel + 39 06 90672342 - Fax +39 06 90672316
>>> E-mail: <giuseppe.mattioli at ism.cnr.it>
>>>
>>> _______________________________________________
>>> Quantum ESPRESSO is supported by MaX
>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>> _______________________________________________
>>> Quantum ESPRESSO is supported by MaX
>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX
>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
>
> GIUSEPPE MATTIOLI
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
> Mob (*preferred*) +39 373 7305625
> Tel + 39 06 90672342 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
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