ghost atoms setting

[xylx9497]

Dear Sir/Madam,
         When I calculate the work function, I need to add ghost atoms. As shown in https://docs.quantumatk.com/tutorials/work_function_tuning/work_function_tuning.html, it's said that "swap the identity of the two ghost atoms, such that the O ghost atom is above the surface O atom and likewise for Mg." This is easy for MgO(100), however,  as for TiN(111) I was confused about the ghost atoms setting (the attachment is TiN111). How to define that the ghost atom is above the surface atom?

[Anders Blom]

You can just make the outermost 1-2 surface layers ghosts (first you might need to make the slab a bit thicker).
Also note that you can get better work function results using the surface Green's function method https://docs.quantumatk.com/tutorials/gf_surface/gf_surface.html#work-function-of-ag-100