> you have to switch to hybrid functionals or GW > formalism (not implemented in QE though).
*both* implemented in QE, for the sake of accuracy...:-) Have a nice we G. On Friday, October 31, 2014 03:17:46 PM Pascal BOULET wrote: > Dear Juanjo, > > As far as I know, metaGGAs are like GGAs for gaps: there are not accurate. > For getting good gaps you have to switch to hybrid functionals or GW > formalism (not implemented in QE though). Depending on what you want to do, > of course, and if you know the gap value you may try this: optimize > with a standard GGA functional, run a nscf calculation and if the gap is not > totally closed up then operate a rigid band shifting for further > properties calculations. This is a bit brute force... > > If you do not know the gap value: run a hybrid single point calculation on > the GGA optimized structure. > > As Yves said, there are not so many options... > > Pascal > > "Juanjo Meléndez" <[email protected]> wrote:Dear Yves Thanks a lot for your > comments. Unfortunately, I need a good description ofgaps to calculate > optical absorption, and hybrid functionals are prohibitive forthe supercells > that I need to use. That is why I started to try withmetaGGA. I will > have a look to the paper you mention (which I did not know, by theway, > thanks!) for more ideas... Take care Juanjo From: Yves Ferro Sent: Friday, > October 31, 2014 10:20 AMTo: PWSCF Forum Subject: Re: [Pw_forum] TB09 > metaGGA DearJuanjo,  From what I can remember:- the meta-GGA kinetic terms > are notsaved in order to restart a nscf, at least up to the 5.0 version,- the > tools for building meta-GGA PPs are not availablein QE.However, I'm > not sure using meta-GGA pseudos will solveyour problem. Meta-GGA are known to > have numerical instabilities such as theones you met, in particular > when then electronic density drop to a very lowlevel as probably in your > ionic crystal LiF, on the contrary with Si and C thatform covalent > structures. You can have a look to this paper you probablyknow:E.R. Johnson, > JCP 131, 0341112009 > I don't believe a cure to you problem exists at themoment, except by changing > the functional to a GGA one. > Best regards, > Yves. > > Le 31 oct. 2014 à 09:26, Juanjo Meléndez a écrit : > Hi Pascal  Thanks for replying. I agree with you that building a > PP consistent with the metaGGA functional would solve most of the > instability problems. But I do not have *any* experience building PPs > (which, by the way, seems to be not trivial to me, even less trivial for > metaGGA), so I followed http://dx.doi.org/10.1016/j.cpc.2013.02.020 and > tried the trick. I was just wondering if any general strategy for > convergence exists.  Regarding point 2, I asked one of the authors of > the aforementioned paper and he declared not the have seen such a > problem before, so I guess that the kinetic terms are not responsible. I > have overcome the problem by using a dense kpoints path already in scf > calculations and calculating the bands without the standard intermediate > nscf run, but it would be nice if the developers could have a look and > check.  Again, thank you very much for your interest.  Juanjo  > Juan J. Meléndez Associate Professor > Department of Physics · University of Extremadura > Avda. de Elvas, s/n 06006 Badajoz (Spain) > Phone: +34 924 28 96 55 > Fax: +34 924 28 96 51 > Email: [email protected] > Web: http://materiales.unex.es/miembros/personal/jj-melendez/Index.html >  From: Pascal BOULET Sent: Thursday, October 30, 2014 7:15 PM > To: PWSCF Forum Subject: Re: [Pw_forum] TB09 metaGGA  hello,  I > have never tried meta-GGA functionals with QE, so I am guessing.  > For point 1, one possible reason is the inadequacy between the pseudo > potential and the functional. I guess you have build a special > pseudopotential for this functional.  Point 2: Could it be because the > meta-GGA kinetic terms are not saved in the checkpoint file and hence > not readable when doing the nscf? > > Pascal   "Juanjo Meléndez" <[email protected]> wrote: > Hi all  I am starting to work with metaGGA functionals in QE (v. > 5.1 + libXc), following Ãric Germaneau and colleaguesâ work > (http://dx.doi.org/10.1016/j.cpc.2013.02.020). I know that metaGGA is > little tested, > but I would be pleased if somebody could answer a couple of questions: >  1) Convergence is quite tricky. Up to know, I got some results > in simple systems using a very small mixing_beta (within 0.01â0.05), not > too many bands (just one or two conduction bands, never converged for > more bands) and restarting from a previously fully converged calculation. I > got results only for carbon, silicon and germanium, never got any > convergence for any binary simple compound (like LiF). Does anyone have > additional hints for metaGGA calculations to converge?  2) In > addition, I get something wrong with nscf calculations. After convergence > of a scf run, I get a list of bands at each k-point, as usual > ânothing strange here. Then I made a path of k-points to get the band > structure and run a nscf calculation. This finishes fine as well, but > the bands are not only different from those from the scf calculations, but > also unrealistically high. I am attaching the input and output > files for both the scf and nscf runs, as well as a couple of eigenval.xml > files taken after nscf. Does anybody know how to manage this? Or > could this be a bug in the code?  Thanks a lot in advance  > Take care  Juanjo  Juan J. Meléndez Associate Professor > Department of Physics · University of Extremadura > Avda. de Elvas, s/n 06006 Badajoz (Spain) > Phone: +34 924 28 96 55 > Fax: +34 924 28 96 51 > Email: [email protected] > Web: http://materiales.unex.es/miembros/personal/jj-melendez/Index.html  > **************************** âAll those who look stupid > actually are, as also are half of those who do not look likeâ (F. de > Quevedo)  **************************** > > Este mensaje no contiene virus ni malware porque la protección de > avast! Antivirus está activa. > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > > >----------------- > > Pascal Boulet > Aix-Marseille University > MADIREL Laboratory > Avenue Normandie-Niemen > 13397 Marseille Cedex 20 > Email: [email protected] > Tel. +33 413 55 18 10 > Fax +33 413 55 18 50 > >  _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > > Este mensaje no contiene virus ni malware porque la protección de > avast! Antivirus está activa. > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > _______________________________________________ > Pw_forum mailinglist > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > > Este mensaje no contiene virus ni malware > porque la protección de avast! Antivirus está activa. > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > > >----------------- > > Pascal Boulet > Aix-Marseille University > MADIREL Laboratory > Avenue Normandie-Niemen > 13397 Marseille Cedex 20 > Email: [email protected] > Tel. +33 413 55 18 10 > Fax +33 413 55 18 50 ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ègaux en droits. Les distinctions sociales ne peuvent être fondèes que sur l'utilitè commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libertè, la propriètè, la sùretè et la rèsistance à l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <[email protected]> http://www.ism.cnr.it/english/staff/mattiolig ResearcherID: F-6308-2012 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
