[Wien] Calculation of Ueff

Mon Mar 27 17:50:55 CEST 2017

Thank you for your answer but i I noticed that Ueff is very sensitive with
the change of RKmax and Kpoint it is for this I evoked this subject abd
 for example
For K = 1 and RKmax 5 i found Ueff = 3.6 eV
But For K = 100 Points and RKmax 8.5 i found Ueff = 5.4 eV

5.4 and 3.6 are relatively far

What I really ask is that the choice of one point is it mandatory? (as is
indicated in the paper of G. K. H. Madsen and P. Novak) or else I have to
force these parameters (a large number of Kpoint and rkmax> 7) which of
these two choices is good?

2017-03-27 17:08 GMT+02:00 Fecher, Gerhard <fecher at uni-mainz.de>:

> you should increase the number of k points (and/or rmtkmax) until the U
> value does not change any longer within the limit that you set yourself
> (say 0.1 eV)
> that is what we call convergence.
>
> .. and as Laurence told, you should remember that you are doing an
> approximation to estimate some value
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von karima
> Physique [physique.karima at gmail.com]
> Gesendet: Montag, 27. März 2017 16:53
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] Calculation of Ueff
>
> Indeed, the calculation converges quickly when I use 100 points with rkmax
> 8 with an iteration number that does not exceed 25 but with one point the
> number of iteration exceeds 100. In your opinion I take 100 points or one
> point as indicated in the paper of G. K. H. Madsen and P. Novak?
>
> thank you in advance
>
> 2017-03-27 16:25 GMT+02:00 Fecher, Gerhard <fecher at uni-mainz.de<mailto:fe
> cher at uni-mainz.de>>:
> "The two calculations converged but with more than 100 iteration (bad
> convergence)"
> ==> did you start them from scratch ? Try to run a calculation with the
> unchanged inputs (regular setting of electron occupation)
>         then use the converged potential to run the calculations with
> changed input files, (I checked some of my old calculations, it never took
> more than 20-25 cycles)
>
> you also may increase the number of k-points (plane waves) and rerun the
> calculation with the preconverged charge densities.
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at<mailto:wien-
> bounces at zeus.theochem.tuwien.ac.at>] im Auftrag von karima Physique [
> physique.karima at gmail.com<mailto:physique.karima at gmail.com>]
> Gesendet: Montag, 27. März 2017 15:41
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] Calculation of Ueff
>
> thank you very much Prof.Laurence Marks for your answer.
>
> 2017-03-27 15:33 GMT+02:00 Laurence Marks <L-marks at northwestern.edu<
> mailto:L-marks at northwestern.edu><mailto:L-marks at northwestern.edu<mailto:L-
> marks at northwestern.edu>>>:
> Many years ago I did some tests of the method in that paper. I remember
> that the value for Ueff one gets does depend a bit upon the parameters
> used, e.g. RKMAX, RMTs, k-points. This is not really a surprise, and the
> value of RKMAX 5 in the original paper was probably a compromise for speed;
> larger RKMAX will localize the electrons more inside the RMTs.
>
> I would suggest that you use parameters representative of what you will
> use in your +U calculations for the estimation of the +U value.
>
> And, always remember that what you are doing is estimating the value for
> an approximate correction of the exchange-correlation potential for use in
> your computational experiments. It is not truly ab-initio, it is a
> heuristic approach.
>
> On Mon, Mar 27, 2017 at 8:20 AM, karima Physique <
> physique.karima at gmail.com<mailto:physique.karima at gmail.com><mailto:
> physique.karima at gmail.com<mailto:physique.karima at gmail.com>>> wrote:
> Thank you for your answer,
>
> The two calculations converged but with more than 100 iteration (bad
> convergence)
>  But in the paper presented by G. K. H. Madsen and P. Novak, they used a
> single point and a value of RKmax = 5,
> Can I force the calculation to 1000 Point for example and RKmax = 8.
>
> 2017-03-27 8:16 GMT+02:00 Fecher, Gerhard <fecher at uni-mainz.de<mailto:fe
> cher at uni-mainz.de><mailto:fecher at uni-mainz.de<mailto:fecher at uni-mainz.de
> >>>:
> your calciulataion is not converged with respect to the number of k-points
> and/or plane waves, is it ?
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at<mailto:wien-
> bounces at zeus.theochem.tuwien.ac.at><mailto:wien-bounces@
> zeus.theochem.tuwien.ac.at<mailto:wien-bounces at zeus.theochem.tuwien.ac.at>>]
> im Auftrag von karima Physique [physique.karima at gmail.com<mailto:
> physique.karima at gmail.com><mailto:physique.karima at gmail.com<mailto:
> physique.karima at gmail.com>>]
> Gesendet: Montag, 27. März 2017 02:09
> An: wien at zeus.theochem.tuwien.ac.at<mailto:wien at zeus.theochem.tuwien.ac.at
> ><mailto:wien at zeus.theochem.tuwien.ac.at<mailto:wien at zeus.theochem.
> tuwien.ac.at>>
> Betreff: [Wien] Calculation of Ueff
>
> Dear Wien2k users,
>
>
> I used the method described by G. K. H. Madsen and P. Novak but I found
> two different values of Ueff when I changed the number of K-point and RKmax
>
> For K=1 Point and RKmax 5 i found Ueff=3.6 eV
> but For K=100 Points and RKmax 8.5 i found Ueff=5.4 eV
>
> Do I use one point only ? otherwise I want to know why I had this
> difference
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> --
> Professor Laurence Marks
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