In the literature[1,2], when calculating GaAs or GaN surfaces by DFT (using package VASP), pseudohydrogen atoms with q=0.75e for the dangling bond of As and N, and q=1.25e for the dangling bond of Ga. I guess it is to make the overall surface charge neutral, but I am not exactly sure how 1.25e and 0.75e are obtained. Do we need to do a Bader analysis or something or is it just a common empirical number that I can use for all cases for GaAs GaN surfaces? Thank you!

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    $\begingroup$ +1 and welcome to our new community! Thank you so much for contributing your question here and we hope to see much more of you in the future!!! Since you said "in the literature [...]", can you show us which papers have this (the 0.75e value of the charge for pseudohydrogen)? $\endgroup$ Commented Sep 13, 2022 at 19:43
  • $\begingroup$ @NikeDattani Thank you! I have just added the references. $\endgroup$
    – SYuan
    Commented Sep 13, 2022 at 20:36
  • $\begingroup$ Have you figured this out yet? Are you still actively in need of an answer? Please update us! $\endgroup$ Commented Jun 13, 2023 at 11:42
  • $\begingroup$ @NikeDattani No I didn't figure it out. I moved on but I am still curious about it if anyone has an answer. $\endgroup$
    – SYuan
    Commented Jun 14, 2023 at 14:30
  • $\begingroup$ I gave my +1 long ago, but now that it has been more than 1 year, can you update us please? Are you still urgently or actively in need of an answer to this question? Did you figure it out? $\endgroup$ Commented Dec 9, 2023 at 17:16


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