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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

I'm quite not sure do understand your question and what you want to
do. However If you use a cell that is 3x3x3 of an other cell where you
know which k-points you want to use, and if you want to use the same
k-points you use in the small cell, do the following:
- notice the coordinates of your previous k-ponts. This are
coordinates in reciprocal space given in multiple of the primitive
vectors of your cell
- convert those coordinates in the new basis given by your new
reciprocal space vectors.
For instance, lets call a1, b1, c1 your unit cells basis vectors ;
a2, b2, c2 the increased vectors (such that a2=3xa1 ...) and denote
with capital vectors the reciprocal space vectors:
you have A1= b1Xc1/(a1.b1Xc1) and A2=b2xc2/(a2.b2Xc2) so A2=A1/3,
etc... If a k-point corrdinates were 1A1+2B1+3C1 they can simply be
express in the new basis as 3A2+6B2+ 9C2...

Hope this help...

regards

PMA

On Sun, May 4, 2008 at 4:14 AM, Andrey Chibisov
<andreichibisov@yandex.ru> wrote:
> Hello, Dear colleagues!
>  I'm new user.
>  How defined k-poin for Si 3x3x3-cell or 3x3x3-cell ? To define correct 
> band gap?
>
>
>  --
>  Andrey Chibisov.
>  Structural Ceramics Laboratory
>  Institute of Geology and Nature Management
>  Far Eastern Branch of Russian Academy of Sciences
>
>



-- 
Pierre-Matthieu Anglade