[Wien] RKMAX and k-mesh

[Torsten Andersen]

Dear Dr. Diaz,

it is not really so simple... but for Ni, Fe, Cu, and some other metals 
I would expect that you should use RKMAX between 8 and 10.5, yes. You 
probably also need a good sampling density in k-space, but it all 
depends on what you want to look at, and how detailed it should be. You 
might want to try to use the "charge convergence" (e.g., runsp_lapw -cc 
0.0001 -so -p) , as it usually also gives a good energy convergence, but 
I would expect it to be difficult to converge the total energy much 
better than about 10 micro-Ry.

Best regards,
Torsten Andersen.

Sergio L. Palacios Diaz wrote:
> Hello Wien community !
> 
> Just a simple question (I think):
> 
> I am running Wien2k for fcc-Ni and performing an analysis similar to
> that done by S. Cottenier for bcc-Fe in his tutorial about LAPW methods.
> The values of the total energy are decreasing for increasing values of
> the RKMAX parameter and from RKMAX=11 the total energy starts to
> increase. So, the optimal value (after S. Cottenier) is RKMAX=10.5
> approx.
> The k-mesh employed consists of 5000 k-points (165 in the irreducible
> part).
> I am wondering the following questions:
> Is there something wrong in using such an unusual RKMAX value (the
> recommended values are from 5 to 9)?
> Is the effect of decreasing RKMAX similar to that of increasing the
> k-mesh?
> 
> Any hint will be welcome.
> 
> Regards,

-- 
Dr. Torsten Andersen        TA-web: http://deep.at/myspace/
AG Hübner, Department of Physics, Kaiserslautern University
http://cmt.physik.uni-kl.de    http://www.physik.uni-kl.de/

Symposium on Excited-state properties of solids, Mannheim 2005:
See: http://cmt.physik.uni-kl.de/XSM05/