[QE-users] Problems with hp.x

Tue Jun 16 19:04:37 CEST 2020

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
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>
>
>
> 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
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> _______________________________________________
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