[QE-users] Problems with hp.x
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Wed Jun 17 17:34:08 CEST 2020
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>)
>>> 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)
>> 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)
> 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>
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