# [Pw_forum] grid of spacing k-vectors

Gabriele Sclauzero sclauzer at sissa.it
Thu May 5 10:50:09 CEST 2011

```You can sample the BZ choosing an appropriate set of k-points inside a primitive cell of the reciprocal lattice. The simplest one, using crystal coordinates, is just a cube of side 1 with a corner in the origin. Then, along each side of the cube you can chose a different grid spacing, which should be inversely proportional to the length (in cartesian metrics) of the corresponding crystal vector, in order to perform an optimal sampling (at least, in my opinion).
Then you can bring all k-points back to the 1st BZ, reduce them to an irreducible set using symmetry, and transform them to cartesian coordinates, if you want.
Perhaps there are other better ways to sample the BZ, but this is the simplest I have in mind and it should be the one used in PWscf (see PW/kpoint_grid.f90).

HTH

GS

Il giorno 05/mag/2011, alle ore 10.01, germaneau ha scritto:

>
> Dear Gabriele,
>
> I have calculated the reciprocal lattice vectors.
>
> I don't get why you said that is the only thing missing.
>
> I have to select k-vectors from the 1st Brillouin zone only, and that's what I can't figure out.
>
> Thank you,
>
>                           Eric.
>
>
>
>
>
> ------------------ 原始邮件 ------------------
> >From: Gabriele Sclauzero <sclauzer at sissa.it>
> >Reply-To: PWSCF Forum <pw_forum at pwscf.org>
> >To: PWSCF Forum <pw_forum at pwscf.org>
> >Subject: Re: [Pw_forum] grid of spacing k-vectors
> >Date: Thu, 5 May 2011 10:01:52 +0200
> >
>
> Dear ric,
>
>    I would say that, for a uniformly spaced grid of k-points, specifying the number of k-points is equivalent to specify the grid spacing (along each basis vector of the reciprocal space independently). Since you know the direct lattice vectors, then you can get the length of the reciprocal lattice vectors, which is the only thing missing.
>
>
> Gabriele
>
>
> Il giorno 05/mag/2011, alle ore 16.14, Eric Germaneau ha scritto:
>
>> Dear all,
>>
>> I'm wondering whether it's possible to generate k-vectors for the Brillouin sampling using
>> a grid of spacing instead of a number of vectors.
>> Thank you,
>>
>>                           ric.
>>
>> --
>> Be the change you wish to see in the world
>> ― Mahatma Gandhi ―
>>
>> Dr. ric Germaneau
>>
>> College of Physical Sciences
>> Beijing 100049
>> China
>>
>> Please, if possible, don't send me MS Word or PowerPoint attachments
>> Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
>> _______________________________________________
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>
>
> § Gabriele Sclauzero, EPFL SB ITP CSEA
>    PH H2 462, Station 3, CH-1015 Lausanne
>
> _______________________________________________
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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