[Pw_forum] K_POINTS automatic

[Giuseppe Mattioli]

Dear Vatankhah
The answer depends also on the kind of system... 111 or 000 are two different ways of sampling the 
first Brillouin zone. 000 indicates that the Monkhorst-Pack mesh is centered on the Gamma point. On 
the contrary, the 111 mesh is shifted from Gamma in order to avoid its inclusion in the mesh, for a 
series of (good) reasons. In other words, you are using two different set of k-points, leading to 
different DOS plots, which should converge when the k-points mesh is rich enough. A partially 
converged mesh will affect metals in a different (stronger) way than insulators or intrinsic 
semiconductors.

In practice, you may want to use a (partially) converged 111 mesh to calculate the potential, to 
optimize the geometry... After this (scf) run you will run a nscf calculation on a richer, well 
converged 000 mesh to calculate your DOS. At least this is what I do...

HTH

Giuseppe



On Monday 03 December 2012 11:44:07 zahra vatankhah wrote:
> Dear Lorenzo,
> Thanks for aswering, but the band structures and also the DOSs are
> different in the two cases even if the Fermi energy is set to zero!
> 
> with regards,
> Vatankhah
> On Mon, Dec 3, 2012 at 12:28 PM, Lorenzo Paulatto <
> 
> lorenzo.paulatto at impmc.upmc.fr> wrote:
> > On 3 December 2012 09:14, zahra vatankhah <vatankhah.z at gmail.com> wrote:
> >> each option (111 or 000) gives different fermi energy, which one is the
> >> correct fermi for the structure?
> > 
> > Dear Zahra,
> > the value Fermi only makes sense relative to the bands structure; if you
> > set the Fermi energy as zero, than the band structure should be the same
> > in the two case.
> > 
> > bests
> > 
> > 
> > --
> > Dr. Lorenzo Paulatto
> > IdR @ IMPMC -- CNRS & Université Paris 6
> > phone: +33 (0)1 44275 084 / skype: paulatz
> > www:   http://www-int.impmc.upmc.fr/~paulatto/
> > mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex
> > 05
> > 
> > 
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   Giuseppe Mattioli                            
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