[Pw_forum] NMR Gipaw Calculations

[Davide Ceresoli]

Dear Alan,
     then probably 0.01 over 520 is ok. You might increase the
cutoff by 5-10 Ry, to improve the f-sum rule. Diagonalization='cg'
in gipaw, is usually faster.

Best,
     Davide


On 09/22/2017 04:11 PM, Ambrozio wrote:
> Dear Davide,
> 
> Thanks for replying,
> 
> I'm working with systems with more than 100 electrons. The systems have 130 or 
> more carbon atoms, it's expensive to me increase the number of k-points. I need 
> optimize the computational cost, do you have a hint in this case?
> 
> Thanks a lot,
> 
> 
> Alan.
> 
> 2017-09-22 7:15 GMT-03:00 Davide Ceresoli <davide.ceresoli at cnr.it 
> <mailto:davide.ceresoli at cnr.it>>:
> 
>     Dear Alan,
>           I would try to reach an absolute error of the order of
>     0.001 on the f-sum rule, for systems up to ~100 electrons.
>     I never investigated whether an absolute or relative error
>     is the right choice.
> 
>     Best regards,
>           Davide
> 
> 
> 
>     On 09/21/2017 07:41 PM, Ambrozio wrote:
>      > Hi dear users and developers,
>      >
>      > I have a question regarding the chemical shielding convergence using
>     Gipaw. As
>      > the best of my knowledge, the f-sum rule parameter is an indicative of the
>      > convergence, corresponding to the number of valence electrons. I use a
>     criterion
>      > of 0.01 for the absolute error in the f-sum rule tensor  principal
>     components.
>      > I'd like to know if this criterion is correct? I mean ... should I take the
>      > absolute error ? or the relative one?
>      >
>      > Regards,
>      >
>      > Alan,
>      >
>      > Federal University of Espirito Santo, Vitoria, Brazil.
>      >
>      > --
>      >
>      > Alan J. Romanel Ambrozio
>      > Bacharel em Física
>      > Mestre em Eng. de Materiais
>      > Doutorando em Física - PPGFis
>      >
>      >
> 
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> 
> 
> 
> -- 
> 
> Alan J. Romanel Ambrozio
> Bacharel em Física
> Mestre em Eng. de Materiais
> Doutorando em Física - PPGFis
> 
> 

-- 
+--------------------------------------------------------------+
   Davide Ceresoli
   CNR Institute of Molecular Science and Technology (CNR-ISTM)
   c/o University of Milan, via Golgi 19, 20133 Milan, Italy
   Email: davide.ceresoli at cnr.it
   Phone: +39-02-50314276, +39-347-1001570 (mobile)
   Skype: dceresoli
   Website: http://sites.google.com/site/dceresoli/
+--------------------------------------------------------------+