[Pw_forum] About k-points

[Lorenzo Paulatto]

On Mon, 05 Mar 2012 00:13:14 +0100, Giovani Faccin  
<faccin.giovani at gmail.com> wrote:

> Dear QE-Users,
>
> Could:
>
> K_POINTS{gamma}
>
> be somehow made equivalent to:
>
> K_POINTS {automatic}
> nk1 nk2 nk3 sk1 sk2 sk3
>
> ? If so, how should one set the nk and sk values above to have the
> calculation performed at gamma only (or if not possible, at least  
> including gamma), while using the second syntax?


The followng syntax performs a calculation with Gamma point sampling:
K_POINTS automatic
  1 1 1  0 0 0

it is however not equivalent to
K_POINTS gamma

The latter uses the fact that wavefunctions at Gamma are (can be set) real  
to save a lot of memory and cpu time. In order to do so it uses several  
tricks that are not compatible with all the post-processing and additional  
codes. Notably, the phonon code does not work with the gamma-only sampling  
tricks.

bests

P.S. note that all the curly braces are not necessary, they also do not  
hurt


-- 
Lorenzo Paulatto IdR @ IMPMC/UPMC CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www.impmc.upmc.fr/~paulatto/
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