Author Topic: Finding BandGap  (Read 13865 times)

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Offline Anders Blom

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Re: Finding BandGap
« Reply #15 on: December 1, 2010, 08:53 »
The ATK.KohnSham module is only relevant for version 2008.10.

In 10.8 you run "atkpython", not "atk".

Offline Anders Blom

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Re: Finding BandGap
« Reply #16 on: December 1, 2010, 10:11 »
Well... it's different in 10.8. The contents of the module are available, but you don't need to import it. But the syntax is a little bit different, you can't just reuse the script from 2008.10.

Offline medeepak

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Re: Finding BandGap
« Reply #17 on: December 1, 2010, 10:17 »
Hi

thanks for the reply
i computed density of states for the file i attached in one of my previous posts
all DOS values are zero
can you kindly tell me what might have been the problem
i am stuck at it for a long time now

Offline Anders Blom

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Re: Finding BandGap
« Reply #18 on: December 1, 2010, 10:26 »
Please post the full complete script that you ran, as well as the log file.

Offline medeepak

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Re: Finding BandGap
« Reply #19 on: December 1, 2010, 11:00 »
Hi
i have attache d my log and script file in this zip file

Offline Anders Blom

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Re: Finding BandGap
« Reply #20 on: December 1, 2010, 11:18 »
The script attached is a molecule. You should compute the density of states for a periodic structure. Even if it technically is possible to do it for a molecule, I don't think the results will be what you are looking for.

Offline medeepak

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Re: Finding BandGap
« Reply #21 on: December 1, 2010, 11:24 »
i calculated its molecular energy spectrum as well
but even in that i get straight lines parallel to x axis

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Re: Finding BandGap
« Reply #22 on: December 1, 2010, 11:30 »
Of course, it's a molecule. All molecules have discrete spectra (sharp levels).

Offline medeepak

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Re: Finding BandGap
« Reply #23 on: December 1, 2010, 11:46 »
Thanks for your replies

Offline medeepak

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Re: Finding BandGap
« Reply #24 on: December 1, 2010, 18:08 »
Hi
 
i created a small distortion in graphene nanoribbon as given in the tutorial

http://www.quantumwise.com/documents/tutorials/BasicGrapheneTutorial/index.html/chap.zigzag_transport.html#id1286600

i want to find its band gap
since its a molecule i cannot run bandstructure calculations and as i understand from discussion even DOS will not give correct results
so how to do it?
kindly help

Offline Anders Blom

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Re: Finding BandGap
« Reply #25 on: December 1, 2010, 20:18 »
If you follow the tutorial, it's a periodic structure, not a molecule. At some point you, by mistake, must be converting the structure to a molecule. Don't :)

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Re: Finding BandGap
« Reply #26 on: December 2, 2010, 06:44 »
Hi

i corrected my mistake and plotted the bandstructure and density of states plot for the structure
the bandstrcuture consists of straight lines and in density of states there is a small peak near zero instead of discontinuity between HOMO and LUMO
what might have been the problem

i have attached my script file and log file with it

 

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Re: Finding BandGap
« Reply #27 on: December 2, 2010, 09:31 »
The bands around the Fermi level are not flat. Results look ok.