[QE-users] Thermal trap ionizations energy evaluation

[Pietro Delugas]

Dear Timofey 

Yes the compensation is between the Hartree term and the Ewald sum works independently from the functional.

Hopefully energy values should not be completely different, just  small differences which should decrease with the distance. 
About using the Makov-Payne corrections directly, I think you need to be a little bit more careful and check directly how the formation energy of the defects behaves increasing the distance between the periodic images. The additional charges around the defects must be localized enough with respect of the supercell size in order that their  electric moments are well defined. In case of HfO2 I guess that together with the charge density the result should also be influenced by the electric displacement density around the charged defects (HfO2 deforms signicantly in response to electric fields).      

Regards 
Pietro 

Sent from Mail for Windows 10

From: Тимофей Перевалов
Sent: Thursday, July 23, 2020 1:40 PM
To: users at lists.quantum-espresso.org
Subject: [QE-users] Thermal trap ionizations energy evaluation

Dear QE users and developers,
I need your help. I am evaluating the thermal ionizations energy of O vacancy in HfO2 as it described the article [PRB 75, 205336, 2007]. One of the calculation formulas (in adapted form) used: (E(perf, q=-1) - E(perf, q=0))  �  (E(def, q= -1) -  E(def, q= 0)).  I know about the compensation background charge presence and I hope that its contribution is cancelled since in formulas, there is a double subtraction. How true is this? I am exploiting B3LYP functional. What should be considered in calculations of this kind?
The resulting values depend on the supercell size. How do I get rid of this? Obviously due to the background charge contribution. The calculations with the Makov-Payne correction (for c-HfO2) give completely different values and also depend on the on the supercell size. 

Sincerely,
Timofey Perevalov
ISP SBRAS, Russia

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