[Pw_forum] convergence problem in scf calculation in rare earth oxide Sm2O3

[Mohammed Khalafalla]

Dear Thomas,
Thank you so much.
Regards
Mohammed



On Thu, Nov 30, 2017 at 3:06 PM Thomas Brumme <thomas.brumme at uni-leipzig.de>
wrote:

> Dear Mohammed,
>
> it's hard to give a general advice also because I didn't do many
> calculation with rare earth elements. Just checking the headers of the
> pseudos from the vlab side it seems both pseudos (LDA and GGA) have the
> same states in valence (l_max=3, number_of_wfc=number_of_proj=8). Did you
> try what they suggest on their side, i.e.:
>
> "In some cases, defining orbital occupations (starting_ns_eigenvalue tag
> in Quantum ESPRESSO) is essential in order to converge calculations."
>
> Maybe this can help to achieve convergence!? Otherwise, it might also help
> to ask them... Or try using the PAW pseudos from the pslibrary without the
> f-states, e.g., Sm.pbe-spdn-kjpaw_psl.1.0.0.UPF (or the ultrasoft one:
> Sm.pbe-spdn-rrkjus_psl.1.0.0.UPF).
>
> And, of course, try what Karim and Ari said:
> - increase ecutrho
> - maybe ferromagnetic starting guess is wrong and you have to go for
> anti-ferromagnetic
>
> Regards
>
> Thomas
>
> On 30.11.2017 11:43, Mohammed Khalafalla wrote:
>
> Dear Thomas,
> Thank you very much for your comments and suggestions.
> You are right the PBE pseudos from
> http://www.vlab.msi.umn.edu/resources/repaw/index.shtml contains
> f-states, but not the LDA ones (I noticed this simply by looking for
> f-states within the pseudo files). So let me double check, shall I use the
> LDA ones instead?
> Thanks ones more.
> Regards,
> Mohammed
>
>
>
> On 29 November 2017 at 11:24, Thomas Brumme <thomas.brumme at uni-leipzig.de>
> wrote:
>
>> Dear Mohammed,
>>
>> adding to the comments of Karim and Ari, I think that you should consider
>> using a pseudo without f-states - of course depending on what you want to
>> predict/calculate. In the end, you use DFT+U to correct for the errors of
>> DFT but putting the f-states into the core is a first approximation to this
>> idea. And the standard ecutrho of 4 times ecutwfc is definitely not enough
>> for PAW potentials if the f shell is included.
>>
>> Regards
>>
>> Thomas
>>
>> On 25.11.2017 20:16, Mohammed Khalafalla wrote:
>>
>> Dear all,
>> I could not achieve scf convergence in Sm2La2O6 (the input file is
>> attached herewith). This was the case even after several 'restart' of the
>> calculation with different pseudpotentials specially for 'O' atom. I guess
>> I used well tested PAW psedu for rare earth from
>> http://www.vlab.msi.umn.edu/resources/repaw/index.shtml
>> I used recommended hubbard potentials and spin polarization, but no
>> change. Generally I found convergence in (Sm,O) system to be difficult. Can
>> you kindly let me know which parameter set-up would determine successful
>> convergence in (Sm,O) system?
>> Regards,
>> Mohammed A. H. Khalafalla (PhD)
>> Taibah University
>> KSA
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing listPw_forum at pwscf.orghttp://pwscf.org/mailman/listinfo/pw_forum
>>
>>
>> --
>> Dr. rer. nat. Thomas Brumme
>> Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
>> Leipzig University
>> Phillipp-Rosenthal-Strasse 31
>> 04103 Leipzig
>>
>> Tel:  +49 (0)341 97 36456
>>
>> email: thomas.brumme at uni-leipzig.de
>>
>>
>
> --
> Dr. rer. nat. Thomas Brumme
> Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
> Leipzig University
> Phillipp-Rosenthal-Strasse 31
> 04103 Leipzig
>
> Tel:  +49 (0)341 97 36456
>
> email: thomas.brumme at uni-leipzig.de
>
> --
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