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Dear All,

I am currently working on calculating the exciton binding energy in Al2O3 systems containing oxygen vacancies. For neutral oxygen vacancies, the approach is straightforward—simply removing the corresponding oxygen atoms in the computational model. However, I am unsure how to properly handle systems with charged oxygen vacancies (e.g., oxygen vacancy with a single positive charge) or cases where both neutral and charged vacancies coexist.

Could you please advise on the specific parameters that should be considered for such calculations?

Thank you in advance for your help!

Best regards,
Jike Wang

Dear Jike Wang,

I moved this topic to the users for users forum because this is not really related to using vasp.
But here are some things you can regard when introducing your charged vacancies:
When you introduce a charged defect (like an oxygen vacancy with a +2 charge), your simulation cell will have a net charge. If you need a charged neutral system which depends on your exact research question you can add electrons with the NELECT tag. If dealing with charged vacancies you might also want to do finite size analysis since the vacancy charge might interact with it's periodic images. For further information on charged vacancies I would check the literature where you will find more information on issues that might arise. Maybe this paper is helpful the authors are using VASP and are dealing with oxygen vacancies. They are even describing their VASP settings https://iopscience.iop.org/article/10.3 ... 786/acd983

All the best Jonathan

Dear Jonathan,

Thanks for your reply! Now I have got the exciton banding energy of Al2O3 with neutral oxygen vacancies, but I don't know how large the exciton binding energy should be to reliably confirm the existence of excitons in Al2O3. Additionally, I want to know if it is possible to perform comparative calculations for the system without excitons. Could you give me some advice? Thanks sincerely!

Best regards,
Jike Wang