The ABINIT Users Mailing List ( CLOSED )

["D. R. Hamann" <drhamann@mat-simresearch.com>]

This is a repeat-send of an initial reply to the post that didn't get 
through for some reason:

Dear JJR,

The "default" is nshiftk  1, shiftk 0.5 0.5 0.5.  This gives an 
efficient zone sampling for some lattices.  For fcc, however, this 
sampling breaks symmetry, which the nshiftk 4 example you have below 
restores.  Your assumption that the shiftk's are added is incorrect.  
The k grid is replicated nshiftk times with shiftk as origins.  For 
hexagonal lattices, only nshiftk 1, shiftk 0.0 0.0 0.5 is appropriate 
(once again, for symmetry-breaking reasons).

D. R. Hamann

Anglade Pierre-Matthieu wrote:
> I think the integration is performed on the "super" grid formed by the
> 4 shifted grid.
>
> On Fri, Mar 21, 2008 at 2:08 PM,  <jjr19@uakron.edu> wrote:
>   
> > > nshiftk 4 will make 4 grid shifted from each others by one of the
> > >       
> >  > provides "shiftk" vector.
> >
> >  So is the Brillouin zone integration done over all the points in all four of 
> > the grids?
> >
> >  BTW, is there any literature specifically on this use of multiple grids. 
> > I've seen plenty on Monkhorst-Pack and on shifting a particular k-point grid, 
> > but not on this particular aspect of generating k-points.
> >
> >     
>
>
>
>   

--
D. R. Hamann
Mat-Sim Research LLC    | Deptartment of Physics
P.O. Box 742            |  and Astronomy
Murray Hill, NJ 07974   | Rutgers University
phone: 908-370-8079     | 732-445-4381

email: drhamann@mat-simresearch.com