## k-point units

Concerns any physical issues arising during the setup step (-i option). This includes problems with symmetries, k/q-point sets, and so on. For technical problems (running in parallel, etc), refer to the Technical forum.

Moderator: Daniele Varsano

### k-point units

Dear Daniele

I am running the setup of yambo code.

1. According to the tutorials, (http://www.yambo-code.org/tutorials/GaSb/bands.php),
Code: Select all
As you can verify from your r-01_init_setup file 28 and 29 are the L and the Gamma point of the Brillouin zone.
*X* K [28] :-0.500000 -0.500000 -0.500000 (rlu) * Comp.s 476 * weight    0.0078
...
*X* K [29] : 0.000000  0.000000  0.000000 (rlu) * Comp.s 531 * weight    0.0020

the k-point unit is in rlu

But from the report file, the last two k-point are:
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*X* K [28] : 0.275869 -0.275869 -0.275869 (cc ) * Comp.s 476 * weight    0.0078
0.250000 -0.250000 -0.250000 (iku)

*X* K [29] : 0.000000  0.000000  0.000000 (cc ) * Comp.s 531 * weight    0.0020
0.000000  0.000000  0.000000 (iku)

Where the k-point units were in cc and iku.

Can you please clarify the relationship between the units, rlu, cc, and iku??
At here the kpoint 28 and 29 are still the L and G point?

2. In addition, in the output of the o.qp file, I get the data like this,
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#
#  K-point    Band       Eo         E-Eo       Sc(Eo)
#
...
29.00000    8.00000    0.00000    0.21758    0.95843
29.00000    9.00000    0.06025    0.65362   -2.36544

How can I sure which band is the VBM and which band is CBM?
Although from the tutorial said that the band 8 is the VBM and 9 is the CBM. But Why 8 is the VBM and 9 is the CBM?

PS. I use the same input as the tutorials
thanks
Wei Li
Institute of theoretical chemistry
Jilin University, PR China
damao4361556

Posts: 39
Joined: Wed Dec 16, 2015 8:11 pm

### Re: k-point units

Dear Eric,
Code: Select all
Can you please clarify the relationship between the units, rlu, cc, and iku??
At here the kpoint 28 and 29 are still the L and G point?

rlu = reciprocal lattice unit
cc= cartesian coordinate
iku = internal k points units

The relation has been already explained in another post:
viewtopic.php?f=9&t=739

28 and 29 are G and L as the definition of high symmetry point is in rlu.

How can I sure which band is the VBM and which band is CBM?
Although from the tutorial said that the band 8 is the VBM and 9 is the CBM. But Why 8 is the VBM and 9 is the CBM?

Yambo by convention set the Kohn-Sham VBM energy to zero, in the report are also reported the direct and indirect gap. From that you can recognize who is VBM and CBM. Of course this is done according to the sampling you have for your ground state.

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

Daniele Varsano

Posts: 2027
Joined: Tue Mar 17, 2009 2:23 pm