Hello,
I'm currently working on point defects, especially oxygen vacancies in YNiO3 and I use VASP.
I first compute the ideal crystal, then I introduced an oxygen vacancy in a 3x3x3 supercell containing 72 Y, 72 Ni, and 215 O. I was wondering if I could introduce some other point defects in this supercell and if I can, how many ? If I can't because of too much interaction, what is the size of a supercell in which I could introduce 2 or more oxygen vacancies ?
Best,
Benjamin
Theoretically you can include as many defect types and numbers as you want, but you have to see if the results make sense in reality! The same for the supercell size !
Hello, thank you for your answer. I know that I can do that but is there an empirical limit to the number of point defect or to the distance between two point defects ?
There is not an easy empirical rule which you can use in this situation. Just based on prior experience, I would guess that putting two oxygen vacancies in a 72 atom metal oxide supercell will result in a strong interaction, varying their formation energies by at least 0.1 eV from the value for a single isolated defect.
But this can vary widely between materials. For example, I did a study once which found that one type of oxygen vacancy became more favorable as more of them were put into a supercell, but an oxygen vacancy at a different crystal site became less favorable as more were put in. I could not have predicted this in advance without testing it.Article Direct observation of apical oxygen vacancies in the high-te...
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