Reference energy in VASP

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jhlee · #1 Post by **jhlee** » Thu Jul 29, 2010 9:23 pm

Dear VASPers,

I have a question about the reference energy in VASP (I know that this issue has been discussed in this board, but I am not completely clear about how the reference energy is defined).

I need to compare the energies of VBM between two similar systems. One has a geometrical distortion with an additional atomic species. For example, one has C only and the other has C and H. I want to see how the distortion shifts VBM.

Since the Kohn-Sham eigenvalues are calculated with respect to a certain reference energy, I believe that I can't make direct comparison between the two VBM energies because the reference energies are different.

I would greatly appreciate if anyone lets me know how to make a right comparison between Kohn-Sham eigenvalues in two different systems. In other words, how can I align the reference energies in the two systems so that I have the same energy zero line?

Thank you all.

alex · #2 Post by **alex** » Fri Jul 30, 2010 9:49 am

You would have to take the vacuum energy as zero. Search for vtotav in that forum. It works for slabs only.

Hth, alex

jhlee · #3 Post by **jhlee** » Fri Jul 30, 2010 2:23 pm

Thanks, Alex.

The problem is: my system is bulk.