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<p><font size="2"><span style="font-size:10pt">> Since it's Cu(I) isn't<br>
> that a closed shell, a d10 system aswell? I was wondering why the<br>
> linear-response theory works in this case but not for Zn2+.</span></font><br>
</p>
<p><br>
</p>
<p>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).</p>
<p><br>
</p>
<p>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).</p>
<p><br>
</p>
<p>HTH</p>
<p><br>
</p>
<p>Iurii<br>
</p>
<p><br>
</p>
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<font size="3" face="'Times New Roman', Times, serif" color="808080">--<br>
Dr. Iurii Timrov<br>
Postdoctoral Researcher<br>
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<font size="3" face="'Times New Roman', Times, serif" color="808080"><font size="3" face="'Times New Roman', Times, serif" color="808080">Swiss Federal Institute of Technology Lausanne (EPFL<font color="808080"><font face="'Times New Roman', Times, serif">)</font></font></font><br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of dv009200@fh-muenster.de <dv009200@fh-muenster.de><br>
<b>Sent:</b> Wednesday, June 17, 2020 11:42:28 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum<br>
<b>Subject:</b> Re: [QE-users] Problems with hp.x</font>
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<div class="PlainText">Thanks again thats for sure very helpful.<br>
<br>
Just out of curiosity I may have one more question: In the paper thats the<br>
basis of the hp.x code (I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B<br>
98, 085127, DOI:10.1103/PhysRevB.98.085127) the Hubbard U parameter of<br>
Cu2O is computed by the linear-response theory. Since it's Cu(I) isn't<br>
that a closed shell, a d10 system aswell? I was wondering why the<br>
linear-response theory works in this case but not for Zn2+.<br>
<br>
Best regards<br>
<br>
Dominik Voigt<br>
<br>
Dominik Voigt<br>
PhD Student University of Applied Sciences Münster<br>
Department of Physical Chemistry<br>
<br>
<br>
<br>
><br>
> Dear Dominik<br>
><br>
>> the method you suggested Giuseppe. I don't quite know whats the 'right'<br>
>> distance between the valence band and the d-band? Can I use experimental<br>
>> data from xps/ups spectra for that matter or do you have other<br>
>> suggestions?<br>
><br>
> Yes, it is actually what I did with ZnO. As I remarked in my previous<br>
> message, it is going to work well if you apply the correction also to<br>
> the S 3p shell, in a DFT+U(Zn,S) fashion. In wurtzite ZnO the strong<br>
> curvature of the Zn 4s conduction band is such that the CB is<br>
> substantially free from delocalization error and it is a good absolute<br>
> reference. If you know the position of the Fermi level (which can<br>
> depend on intrinsic defects in real samples) with respect to the CB,<br>
> then you can reasonably estimate the position of the Zn 3d band.<br>
> I hope I've not added entropy...<br>
> Best<br>
> Giuseppe<br>
><br>
> Quoting dv009200@fh-muenster.de:<br>
><br>
>> Thanks all for the helpful comments and interesting papers. I'm fine<br>
>> correcting the delocalization error of the Zn 3d states 'semiempirical'<br>
>> by<br>
>> the method you suggested Giuseppe. I don't quite know whats the 'right'<br>
>> distance between the valence band and the d-band? Can I use experimental<br>
>> data from xps/ups spectra for that matter or do you have other<br>
>> suggestions?<br>
>><br>
>> Best regards<br>
>><br>
>> Dominik Voigt<br>
>><br>
>> Dominik Voigt<br>
>> PhD Student University of Applied Sciences Münster<br>
>> Department of Physical Chemistry<br>
>><br>
>><br>
>><br>
>>> Dear All,<br>
>>><br>
>>><br>
>>> Giuseppe is right, this is a limitation of the current implementation<br>
>>> of<br>
>>> the linear-response theory to compute Hubbard parameters for<br>
>>> closed-shell<br>
>>> systems (like ZnO, ZnS, etc.). This "limitation" is known, and there is<br>
>>> some comment about this in q-e/HP/Doc/README. Please check this paper<br>
>>> for<br>
>>> more details:<br>
>>> <<a href="https://aip.scitation.org/doi/10.1063/1.4869718">https://aip.scitation.org/doi/10.1063/1.4869718</a>><br>
>>><br>
>>> <a href="https://aip.scitation.org/doi/10.1063/1.4869718">https://aip.scitation.org/doi/10.1063/1.4869718</a><br>
>>><br>
>>><br>
>>> The developers of the HP code are planning to investigate this issue in<br>
>>> more detail, and hopefully we will come out with some solution in the<br>
>>> near<br>
>>> future.<br>
>>><br>
>>><br>
>>> Best regards,<br>
>>><br>
>>> Iurii<br>
>>><br>
>>><br>
>>> --<br>
>>> Dr. Iurii Timrov<br>
>>> Postdoctoral Researcher<br>
>>> STI - IMX - THEOS and NCCR - MARVEL<br>
>>> Swiss Federal Institute of Technology Lausanne (EPFL)<br>
>>> CH-1015 Lausanne, Switzerland<br>
>>> +41 21 69 34 881<br>
>>> <a href="http://people.epfl.ch/265334">http://people.epfl.ch/265334</a><br>
>>> ________________________________<br>
>>> From: users <users-bounces@lists.quantum-espresso.org> on behalf of<br>
>>> Giuseppe Mattioli <giuseppe.mattioli@ism.cnr.it><br>
>>> Sent: Monday, June 15, 2020 10:55:59 PM<br>
>>> To: Quantum ESPRESSO users Forum<br>
>>> Subject: Re: [QE-users] Problems with hp.x<br>
>>><br>
>>><br>
>>> Dear Dominik<br>
>>> I suppose that the problem is not in hp.x, but in the application of<br>
>>> the linear-response method itself to Zn(2+). Zn(2+) is a d10<br>
>>> transition metal, with the 3d band fully occupied. In ZnO, e.g., the<br>
>>> Zn 3d band is quite narrow and placed below the O 2p valence band, and<br>
>>> I suppose that the same holds for ZnS, with the Zn 3d band pushing up<br>
>>> the S 3p band. When you apply the LR method to Zn, you compute<br>
>>> quantities such as d(alpha)/dn, where alpha is the (small)<br>
>>> perturbation and n is the occupation number of d orbitals on site I<br>
>>> (see International Journal of Quantum Chemistry 2014, 114, 14 for<br>
>>> details). If the shell is full, then you can perturb whatever you want<br>
>>> but you will never obtain more than the full occupation of the shell<br>
>>> that you already have in the unperturbed system. This is likely the<br>
>>> reason for the crazy values of LR U you obtain. If you want to correct<br>
>>> the strong delocalization error of the Zn 3d narrow band within the<br>
>>> DFT+U formalism, then you must use a "semiempirical" approach,<br>
>>> choosing, e.g., the U value that places the Zn 3d shell at the correct<br>
>>> distance from the valence band maximum. In this case, I would<br>
>>> recommend the use of a second +U correction on the S 3p shell, which<br>
>>> should ensure a good recovery of the ZnS band gap. I've satisfactorily<br>
>>> used this scheme in the case of ZnO in several publications, from<br>
>>> which you may want to take inspiration (Adv. Energy Mater. 2014, 4,<br>
>>> 1301694).<br>
>>> HTH<br>
>>> Giuseppe<br>
>>><br>
>>> Quoting dv009200@fh-muenster.de:<br>
>>><br>
>>>> Hello everyone,<br>
>>>><br>
>>>> I'm trying to calculate the hubbard u parameter for Zn in Zinc sulfide<br>
>>>> (sphalerite structure) with the help of the hp.x code. The<br>
>>>> calculations<br>
>>>> terminate normally without any errors. The problem is that I get<br>
>>>> (presumably) way too high values for U that also won't converge (if I<br>
>>>> take<br>
>>>> the value I got from a one-shot calculation and plug it in the SCF<br>
>>>> input<br>
>>>> and then redo the HP calculation).<br>
>>>><br>
>>>> For example in the first step I calculate a U = 75.7035 in the second<br>
>>>> iteration I get U = 804.2405 and in the third U = 30999.2684.<br>
>>>><br>
>>>> This seems unreasonable considering that the calculations for the<br>
>>>> provided<br>
>>>> examples in the 'HP' folder work fine and converge fast without such a<br>
>>>> massive change to a certain value for U using the above described<br>
>>>> scheme.<br>
>>>><br>
>>>> Has someone an idea what is causing this trouble in my system? I<br>
>>>> already<br>
>>>> tried different PPs, functionals, U_projection_type, thresholds and k<br>
>>>> and<br>
>>>> q point grids all without success.<br>
>>>><br>
>>>> Below is my input for the scf and hp calculation<br>
>>>><br>
>>>> SCF-input:<br>
>>>>  &control<br>
>>>> calculation='scf'<br>
>>>> restart_mode='from_scratch',<br>
>>>> pseudo_dir = '/home/dominik/codes/QE6.5/pseudo/'<br>
>>>> outdir='/home/dominik/codes/QE6.5/tempdir/'<br>
>>>> prefix='zns'<br>
>>>> /<br>
>>>> &SYSTEM<br>
>>>> ibrav = 2<br>
>>>> celldm(1)=10.291937439<br>
>>>> nat = 2<br>
>>>> ntyp = 2<br>
>>>> ecutwfc = 60.0<br>
>>>> ecutrho= 720.0<br>
>>>> lda_plus_u = .true.<br>
>>>> lda_plus_u_kind = 0<br>
>>>> U_projection_type = 'atomic'<br>
>>>> Hubbard_U(1) = 1d-8<br>
>>>> /<br>
>>>> &electrons<br>
>>>> mixing_beta=0.7<br>
>>>> conv_thr=1d-15<br>
>>>> /<br>
>>>> ATOMIC_SPECIES<br>
>>>> Zn 65.39 Zn.pbe-dn-rrkjus_psl.0.2.2.UPF<br>
>>>> S 32.07 S.pbe-n-rrkjus_psl.0.1.UPF<br>
>>>> ATOMIC_POSITIONS {alat}<br>
>>>> Zn 0.000000 0.000000 0.000000<br>
>>>> S 0.250000 0.250000 0.250000<br>
>>>> K_POINTS automatic<br>
>>>> 12 12 12 0 0 0<br>
>>>><br>
>>>><br>
>>>> HP-input:<br>
>>>> &inputhp<br>
>>>> prefix='zns'<br>
>>>> outdir='/home/dominik/codes/QE6.5/tempdir/'<br>
>>>> nq1 = 2<br>
>>>> nq2 = 2<br>
>>>> nq3 = 2<br>
>>>> conv_thr_chi = 1.0d-10<br>
>>>> iverbosity =2<br>
>>>> /<br>
>>>><br>
>>>><br>
>>>> Best regards<br>
>>>><br>
>>>><br>
>>>> Dominik Voigt<br>
>>>><br>
>>>> Dominik Voigt<br>
>>>> PhD Student University of Applied Sciences Münster<br>
>>>> Department of Physical Chemistry<br>
>>>><br>
>>>> _______________________________________________<br>
>>>> Quantum ESPRESSO is supported by MaX<br>
>>>> (<a href="http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso</a>>)<br>
>>>> users mailing list users@lists.quantum-espresso.org<br>
>>>> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
>>><br>
>>><br>
>>><br>
>>> GIUSEPPE MATTIOLI<br>
>>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
>>> Via Salaria Km 29,300 - C.P. 10<br>
>>> I-00015 - Monterotondo Scalo (RM)<br>
>>> Mob (*preferred*) +39 373 7305625<br>
>>> Tel + 39 06 90672342 - Fax +39 06 90672316<br>
>>> E-mail: <giuseppe.mattioli@ism.cnr.it><br>
>>><br>
>>> _______________________________________________<br>
>>> Quantum ESPRESSO is supported by MaX<br>
>>> (<a href="http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso</a>>)<br>
>>> users mailing list users@lists.quantum-espresso.org<br>
>>> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
>>> _______________________________________________<br>
>>> Quantum ESPRESSO is supported by MaX<br>
>>> (<a href="http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso</a>)<br>
>>> users mailing list users@lists.quantum-espresso.org<br>
>>> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
>><br>
>><br>
>> _______________________________________________<br>
>> Quantum ESPRESSO is supported by MaX<br>
>> (<a href="http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso</a>)<br>
>> users mailing list users@lists.quantum-espresso.org<br>
>> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
><br>
><br>
><br>
> GIUSEPPE MATTIOLI<br>
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
> Via Salaria Km 29,300 - C.P. 10<br>
> I-00015 - Monterotondo Scalo (RM)<br>
> Mob (*preferred*) +39 373 7305625<br>
> Tel + 39 06 90672342 - Fax +39 06 90672316<br>
> E-mail: <giuseppe.mattioli@ism.cnr.it><br>
><br>
> _______________________________________________<br>
> Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu/quantum-espresso">www.max-centre.eu/quantum-espresso</a>)<br>
> users mailing list users@lists.quantum-espresso.org<br>
> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
<br>
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