QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: sukhito teh on December 18, 2023, 13:56
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Dear developers and users,
Do you know any paper that explain how DFT-PPS method works or use the method to correct electronic bandgap? I tried but unable to find any related paper. Or is there a general guide on how to optimize the parameters?
Thank you for your time.
Best regards,
Sukhito
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You can read more about it here: https://docs.quantumatk.com/tutorials/dft_half_pps/dft_half_pps.html. In short, it's an attempt to bring some aspect of empirical pseudopotentials into DFT, but instead of a scissor operator acting on the final band structure (which wouldn't work in Ge for instance) there are shifts being applied within the self-consistent cycle. It does require empirical tuning, i.e. you should know the band gap from experiments to tune the parameters.
We implemented this method quite a long time ago, and honestly have not found much use for it. Since then, we have added DFT+1/2 which seems to be a more robust and general scheme, where the same parameters seem to work for many different systems, although you can fine tune them if you do know the band gap. And of course HSE06 and other hybrid functionals which perform really well in LCAO, and which can be truly predictive of the band gaps of unknown materials.
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You can read more about it here: https://docs.quantumatk.com/tutorials/dft_half_pps/dft_half_pps.html. In short, it's an attempt to bring some aspect of empirical pseudopotentials into DFT, but instead of a scissor operator acting on the final band structure (which wouldn't work in Ge for instance) there are shifts being applied within the self-consistent cycle. It does require empirical tuning, i.e. you should know the band gap from experiments to tune the parameters.
We implemented this method quite a long time ago, and honestly have not found much use for it. Since then, we have added DFT+1/2 which seems to be a more robust and general scheme, where the same parameters seem to work for many different systems, although you can fine tune them if you do know the band gap. And of course HSE06 and other hybrid functionals which perform really well in LCAO, and which can be truly predictive of the band gaps of unknown materials.
Thank you, I would look into DFT-1/2; HSE06 is good, I have found good results with them, the ADMM can even speed up HSE calculation so the efficiency is comparable to regular DFT. However ADMM is not compatible to NEGF, so I am looking for alternatives.
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Correct, but HSE with LCAO is still reasonable for NEGF, we have tested it with 1000+ atoms. Needs a lot of memory though, that might be an even larger benefit of ADMM which, for now, we cannot obtain in NEGF,