On 08/03/2011 04:18 AM, Guangping Zhang wrote:
Dear Hongyi,
Thank you very much for you reply.
I have known the sampling is done over the reciprocal space. But I am
not sure how to understand the kgrid_Monkhorst_Pack used in SIESTA.
I used to think the first three integers in each line stand for the
number points used for each reciprocal vectors.
If my understand is right, what is the difference between the following
two way to specify the k sampling.
%block LatticeVectors
a 0.0 0.0
0.0 b 0.0
0.0 0.0 c
%endblock LatticeVectors
%block kgrid_Monkhorst_Pack
4 0 0 0.0
0 4 0 0.0
0 0 1 0.0
%endblock kgrid_Monkhorst_Pack
In this way, 4, 4 and 1 k point are used along each reciprocal vector
which has the same direciton with its corresponding real space vector.
But if I specify like the following:
%block kgrid_Monkhorst_Pack
4 4 1 0.0
0 0 0 0.0
0 0 0 0.0
%endblock kgrid_Monkhorst_Pack
Does it have the same meaning as the first way?
I have read the manual for many times but I yet have difficulties in
understanding it.
Please do help me or give some instructions.
Best
Guangping
2011-08-03
------------------------------------------------------------------------
Guangping Zhang
------------------------------------------------------------------------
发件人: Hongyi Zhao <[email protected]>
发送时间: 2011-08-03 14:05
主 题: Re: [SIESTA-L] About k_sampling
收件人: [email protected]
On 08/02/2011 11:12 PM, Guangping Zhang wrote:
> Dear Siesta users:
> I now have a puzzle on the k point sampling.
> Before, I usually use a cubic in real space,
> for example:
> %block LatticeVectors
> a 0.0 0.0
> 0.0 b 0.0
> 0.0 0.0 c
> %endblock LatticeVectors
> So its corresponding reciprocal space is also a cubic:
> a' 0.0 0.0
> 0.0 b' 0.0
> 0.0 0.0 c'
> when I use the k sampling for this kind cell
> %block kgrid_Monkhorst_Pack
> 4 0 0 0.0
> 0 4 0 0.0
> 0 0 1 0.0
> %endblock kgrid_Monkhorst_Pack
> I think it means 4, 4 and 1 k point will be used along a', b' and c'
> will be used. (Am I right?)
> But if I use a non-cubic cell,
> for example:
> %block LatticeVectors
> a1 a2 0.0
> b1 b2 0.0
> 0.0 0.0 c
> %endblock LatticeVectors
> so the corresponding reciprocal space is also a non-cubic:
> maybe like the following:
> a1' a2' a3' (say Vector1)
> b1' b2' b3' (say Vector2)
> c1' c2' c3' (say Vector3)
> If I also use a K point sampling like:
> %block kgrid_Monkhorst_Pack
> 4 0 0 0.0
> 0 4 0 0.0
> 0 0 1 0.0
> %endblock kgrid_Monkhorst_Pack
> This time, are 4, 4 and 1 the k points along the reciprocal Vector1,
> Vector2 and Vector3 respectively?
> Maybe, my discription could make someone confused.
> In other words, is the block kgrid represented in real space lattice
> vectors or in reciprocal space vectors or just in cartesian coordinates?
> Any reply will be appreciated.
In this siesta, there are two methods to initialize the kgrid:
kgrid_cutoff
and
kgrid_Monkhorst_Pack
When I don't know how to set the block kgrid_Monkhorst_Pack, I always
use a series of kgrid_cutoff to let the siesta find the most appropriate
kgrid_Monkhorst_Pack for the system.
Regards
> Best
> Guangping
> 2011-08-03
> ------------------------------------------------------------------------
> Guangping Zhang
See here for some notes:
http://cmt.dur.ac.uk/sjc/thesis_mcg/node24.html
Regards
--
Hongyi Zhao <[email protected]>
Institute of Semiconductors, Chinese Academy of Sciences
GnuPG DSA: 0xD108493
--
Hongyi Zhao <[email protected]>
Institute of Semiconductors, Chinese Academy of Sciences
GnuPG DSA: 0xD108493
