Thank you very much for your detailed response. 2017-03-28 3:48 GMT+02:00 Gavin Abo <gs...@crimson.ua.edu>:
> The NiO example [1] with 1 k-point gave about 6 eV with the NiO_+.5-1 > calculation taking about 36 cycles [2,3]. N.B. [4], this is with 2.00 and > not 20.3 in case.in1. I believe the 20.3 in the paper may be a > typographical error. At the bottom of [1], there is the statement: > > Usually, it is better to just set the d energy 2-4 Ry above the Fermi > level. > > The Fermi level is not known when starting the calculation, but a small > value of about 0 is likely a reasonable assumption. So let Fermi level = > 0. Taking the lower value of 2 Ry from the statement above. So took 2.00 > for case.in1. I think the Fermi level obtained after the calculation was > about 0.5. If you round that down, it becomes zero. So it seems the 0 was > likely an okay starting assumption. > > I suspect 1 k-point and 5 RKmax wouldn't be used if it was a proper > calculation, but the paper is an example such that it was likely chosen for > speed [5]. > > For example, it looks like 100 k-points and 5.7 RKmax (instead of 1 > k-point and 5 RKmax) were used in G. K. H. Madsen and P. Novak calculation > for Fe3O4 [6]. > > Keep in mind that the Ueff values obtained from the Constrained method are > known to be of questionable accuracy [7]. > > Rather than your two choices below, it is better to do convergence tests > [8-12]. > > [1] http://susi.theochem.tuwien.ac.at/reg_user/textbooks/Constraint_U.pdf > [2] http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac. > at/msg14460.html > [3] http://wien2k-algerien1970.blogspot.com/2016/08/how-to- > calculate-u-parameter-in-nickel.html > [4] https://en.wikipedia.org/wiki/Nota_bene > [5] http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac. > at/msg15593.html > [6] https://arxiv.org/abs/cond-mat/0412560v1 > [7] http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac. > at/msg12429.html > [8] http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac. > at/msg15596.html > [9] http://wien2k-algerien1970.blogspot.com/2016/08/kpoint- > convergence-test.html > [10] https://www.beilstein-journals.org/bjnano/content/ > supplementary/2190-4286-2-45-S1.pdf > [11] http://www.mail-archive.com/wien%40zeus.theochem.tuwien. > ac.at/msg01700.html > [12] http://www.mail-archive.com/wien%40zeus.theochem.tuwien. > ac.at/msg08186.html > > On 3/27/2017 9:50 AM, karima Physique wrote: > > 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 > > > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: http://www.mail-archive.com/ > wien@zeus.theochem.tuwien.ac.at/index.html > >
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