[Pw_forum] shift kpoint

[Lorenzo Paulatto]

In data 21 agosto 2009 alle ore 11:22:20, ali kazempour  
<kazempoor2000 at yahoo.com> ha scritto:

> Dear all
> In principle ,where the shift of kpoints is important? I mean which  
> information should we loose when we don't use from shift in our kpoint  
> mesh?

You don't loose any information, it's just that a shifted grid makes the  
calculation converge faster w.r.t the number of kpoints. This is normally  
only true after applying symmetry operation to reduce the number of  
kpoints.

> [...] does it mean that symmetry reduces this set to a set of points in  
> the irreducible part of BZ?

Exactly.

There are some exceptions though, e.g. using Gamma point (and only Gamma  
point) is the only meaningful choice for isolated systems.

regards

-- 
Lorenzo Paulatto
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