VASP Forum

Hi,

I am trying to compare the DOS plots of a Co surface and a Co surface (system A) with a CoO island on top of it (system B). Is it valid to align these DOS plots by the using the difference in core electron energies? For example, if a bulk like Co 1s orbital in system B is -1.0 eV relative to the same Co 1s orbital in system A, should I shift the entire DOS of system B by +1.0 eV to align it to system A?
I'm also not sure if I should just align to the vacuum potential, but then what is the best practice if there is no vacuum in the system, i.e., for bulk cells?

Hello,

I am still in the process of learning this as well. For you since you are working with metals, mayhaps someone with more experience can correct me if I am wrong.

What I know so far is that surface slabs is the way to go for band alignment since the vacuum is an appropriate choice for aligning the DOS. We 1) find out the vacuum level of the slab as laid out in this work function tutorial. It's important to note that different surfaces will report different vacuum levels, and we shall align it in the final analysis.

Then, 2) since you are working on the metal I assume we will find the difference between the vacuum level and the Fermi energy of the surface.

3) Lastly, we set the vacuum references as 0 eV.

This is what I know so far about DOS alignment using the vacuum level.

On another note, I am curious about the core electron energies method you mentioned. Can I know from which resource did you read up on this? Thank you.

Please let me know if there is anything unclear.
Best,