how to input k-point

Rieska Amilia

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Mar 11, 2016, 12:10:52 AM3/11/16

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i need help..... i looking for band gap from silicon nanotube, i need to input k-point to get accurate band gap, because my lecture said that if there is no k-point the velue not be accurate. i have tried to input k-point, but error.... i need help please...

regards,

Rieska Amilia
Surabaya, Indonesia

Rieska Amilia

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Mar 11, 2016, 12:15:25 AM3/11/16

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this is my file

Ekpo.out

Ekpo.inp

Conrad

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Mar 11, 2016, 5:02:46 AM3/11/16

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Dear Rieska,

Which version of CP2K are you using? Your error would suggest that you're using an older version. Kpoints are a new and in-development feature, available in 3.0 and the trunk version.

Your lecturer is correct also. Additionally, in your sample input, it looks like you're requesting only Gamma point sampling ( SCHEME GAMMA) which won't necessarily give you an accurate gap. I don't know about silicon nanotubes, but in silicon crsytal, the band gap is famously "indirect" so gamma point sampling can't capture this, I believe.

Best regards,
Conrad

Rieska Amilia

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Mar 13, 2016, 9:22:33 PM3/13/16

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thanks for your replay mr. conrad
i use v2.4, how can i upgrade my cp2k version? and if i'm not use gamma point, what i need to get it(k-point)?

best regards,
Rieska

Conrad

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Mar 14, 2016, 6:05:25 AM3/14/16

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Dear Rieska,

Instructions on how to compile CP2K are here:

https://www.cp2k.org/howto:compile

If you have a specific issue with compilation, search in the Google Group - there's many threads about these sort of things.

Regarding the k-points, have a look at some of the big solid state texts like "Introduction to Solid State Physics", by Kittel. The gamma point is one specific "special" k-points. When your professor says you need k-points to get an accurate band gap, he's getting at the fact that you need to sample many k-points, not just the gamma point. When you see band structure plots, these are plots of the energy levels over many k-points, tracing a path through the Brillouin zone.

I'm not sure what stage the k-point development is at in CP2K. Hopefully someone will jump in and help me here! I think in 3.0, you can generate a grid of k-points, using Monkorst-Pack or a regular grid. but I'm not sure if you can specify particular points, yet. The keyword is clearly there in the manual but I've not used it or tested it.

Iain Bethune

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Mar 14, 2016, 6:12:44 AM3/14/16

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There is a summary of the current capabilities of the k-points code here:

https://www.cp2k.org/faq:kpoints

Basically, you can get total energies, forces, stresses, but not a band structure.

- Iain

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Conrad

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Mar 14, 2016, 8:09:49 AM3/14/16

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Thanks Ian,

The FAQ should have been the first place I looked!

Best regards,
Conrad

Rieska Amilia

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Mar 14, 2016, 11:41:32 PM3/14/16

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thanks mr.Iain
then what i have to input so that i get band structure?

best regards,
Rieska

Rieska Amilia

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Mar 14, 2016, 11:43:50 PM3/14/16

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thanks mr. Conrad

can you use version 3.0? i feel so difficult to install it,sir

best regards,
Rieska Amilia

Iain Bethune

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Mar 15, 2016, 5:14:44 AM3/15/16

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Sorry but at present you can’t (without non-trivial code changes).

- Iain

--

Iain Bethune
Project Manager, EPCC

Email: ibet...@epcc.ed.ac.uk
Twitter: @IainBethune @PrimeGrid @CP2Kproject
Web: http://www2.epcc.ed.ac.uk/~ibethune
Tel/Fax: +44 (0)131 650 5201/6555
Mob: +44 (0)7598317015
Addr: 2404 JCMB, The King's Buildings, Peter Guthrie Tait Road, Edinburgh, EH9 3FD

Rieska Amilia

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Mar 21, 2016, 3:45:13 AM3/21/16

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thank you sir of your help...
but anyway, can i use version 2.6.1 for input k-point?

best regards,
rieska amilia

Conrad

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Mar 21, 2016, 4:03:13 AM3/21/16

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No, it was only implemented later.

Rieska Amilia

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Mar 21, 2016, 4:19:02 AM3/21/16

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thanks sir...
but i see on cp2k.org specificationof 2.6.1 is available for input k-point?

best regards,
rieska

Conrad

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Mar 21, 2016, 4:49:51 AM3/21/16

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Rieska,

As Ian Bethune has said already, the capabilities for the latest version are detailed in:

https://www.cp2k.org/faq:kpoints

Anything in 2.6 will be a lesser version of the above.

Best regards,
Conrad

Michael Banck

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Mar 21, 2016, 6:21:57 PM3/21/16

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Hi,

On Mon, Mar 21, 2016 at 01:19:02AM -0700, Rieska Amilia wrote:
> but i see on cp2k.org specificationof 2.6.1 is available for input k-point?

A foundational K-Points framework shipped with 2.6.1 for some
semi-emprical methods, but if you want to use DFT (Quickstep), that is
only available from 3.0 on.

Michael

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