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[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

Hmmm, this is very interesting! It looks like it depends on the kpoint sampling including the K point or not (1/3 1/3 in recip space)... This is of course the only point on the Fermi surface. However the residuals are not only bad at K... So it's the combination of having the K point and not having the appropriate symmetrizations, but I don't know how this plays in to the conditionning of the convergence.

Matthieu

On Wed, Mar 4, 2009 at 6:08 PM, Anglade Pierre-Matthieu <anglade@gmail.com> wrote:

Hi Matthieu,

Have you noticed that there is two case depending on your k-point mesh ?
In the wrong case, obtained with meshes like 36 36 1, 12 12 1, 9 9 1,
6 6 1, the potential residual you get is a function of the number of
k-point you use :The less k-point,  the bigger the vres2.
Yet If one uses a single k-point or some other meshes (tried 211, 221,
441, 551, 771, 881, 35 35 1)  everythings converge fine.

If one or a few k-point were getting a  "shift"  because of bad
application of symmetries in the nonsymmop case,  don't you think it
could lead to this behavior ?

Have you already explored this idea ?

Regards

PMA

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF) 
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