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General Questions and Answers / Re: Thin Film Meta-GGA C-parameter
« on: August 27, 2018, 17:33 »
Thank you for your response! It clears up a lot for me.
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General Questions and Answers / Thin Film Meta-GGA C-parameter
« on: August 23, 2018, 16:54 »
Hi!
In the tutorial for using meta-GGA on thin films (https://docs.quantumwise.com/v2017/tutorials/inas_2d_mgga/inas_2d_mgga.html)
You say: "For confined systems one must first determine an appropriate value for c for the corresponding bulk system. This can be done either self-consistently or by fitting the c-parameter..."
I'm just wondering if you have a reference that justifies using the same c parameter for the thin films as in bulk?
Regards,
Conor
In the tutorial for using meta-GGA on thin films (https://docs.quantumwise.com/v2017/tutorials/inas_2d_mgga/inas_2d_mgga.html)
You say: "For confined systems one must first determine an appropriate value for c for the corresponding bulk system. This can be done either self-consistently or by fitting the c-parameter..."
I'm just wondering if you have a reference that justifies using the same c parameter for the thin films as in bulk?
Regards,
Conor
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General Questions and Answers / Re: SnGe with mGGA
« on: August 31, 2016, 20:11 »
Thank you all for the assistance! I'll look in to the methods you've suggested. 
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General Questions and Answers / Re: SnGe with mGGA
« on: August 22, 2016, 12:04 »
I've attached the input script for the calculation, as well as the standard output file.
Relaxation aside, I'm not sure it's wise to allow the c parameter to be determined self consistently, as when this is done with germanium an inaccurate representation of the band structure is obtained.
There's more info on that in this forum post: http://quantumwise.com/forum/index.php?topic=3202.0
Thanks for the attention so far!
Relaxation aside, I'm not sure it's wise to allow the c parameter to be determined self consistently, as when this is done with germanium an inaccurate representation of the band structure is obtained.
There's more info on that in this forum post: http://quantumwise.com/forum/index.php?topic=3202.0
Thanks for the attention so far!
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General Questions and Answers / Re: SnGe with mGGA
« on: August 12, 2016, 13:01 »
In the literature, SnGe isn't supposed to become semimetallic until a much higher (20-25%) concentration of tin. For values of 6.5 %, the band gap is not even expected to transition from indirect to direct.
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General Questions and Answers / SnGe with mGGA
« on: August 3, 2016, 18:29 »
Hi,
So I'm trying to use meta-GGA to describe the band structure of tin germanium.
My first step was to look at the individual elements. I achieved a realistic band structure using the HGH solution suggested by Umberto in this thread: http://quantumwise.com/forum/index.php?topic=3202.0
Band gaps:
Γ-L: 0.630 eV
Γ-Γ: 0.846 eV
For tin, using these same parameters (c value and basis sets) I achieved a semimetallic tin structure.
I then created a 16 atom cell of 15 germanium atoms and 1 tin atom. (again using the same c value and basis sets), but the obtained band structure showed semimetallic behavior, instead of showing the band gap which is expected at this low (6.25%) concentration of tin.
Is this a limitation of meta GGA, or am I missing something?
All help would be much appreciated.
Regards,
Conor
So I'm trying to use meta-GGA to describe the band structure of tin germanium.
My first step was to look at the individual elements. I achieved a realistic band structure using the HGH solution suggested by Umberto in this thread: http://quantumwise.com/forum/index.php?topic=3202.0
Band gaps:
Γ-L: 0.630 eV
Γ-Γ: 0.846 eV
For tin, using these same parameters (c value and basis sets) I achieved a semimetallic tin structure.
I then created a 16 atom cell of 15 germanium atoms and 1 tin atom. (again using the same c value and basis sets), but the obtained band structure showed semimetallic behavior, instead of showing the band gap which is expected at this low (6.25%) concentration of tin.
Is this a limitation of meta GGA, or am I missing something?
All help would be much appreciated.
Regards,
Conor
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