[Pw_forum] TB09 metaGGA

[Juanjo Meléndez]

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: melendez at unex.es
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" <melendez at unex.es> wrote: 
  Hi all

  I am starting to work with metaGGA functionals in QE (v. 5.1 + libXc), following Èric Germaneau and colleagues’ 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 0.01–0.05), 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 –nothing 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: melendez at unex.es
  Web: http://materiales.unex.es/miembros/personal/jj-melendez/Index.html

  ****************************
  “All those who look stupid actually are, as also are half of those who do not look like” (F. de Quevedo)

  ****************************



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>-----------------
Pascal Boulet
Aix-Marseille University 
MADIREL Laboratory
Avenue Normandie-Niemen 
13397 Marseille Cedex 20 
Email: pascal.boulet at univ-amu.fr 
Tel. +33 413 55 18 10 
Fax +33 413 55 18 50




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