# The upper limit for the atomic adsorption energy value on a slab surface?

I want to adsorb atomic oxygen on a slab surface.

The adsorption energy I am calculating is around -10 eV. Which seems higher to me than I expected.

My question is this: Is this value reasonable or is there some issue in my calculation?

To address the question in the title, I went to Catalysis-Hub and sorted the computed energies from most exothermic to most endothermic. Ignoring the C (g) entries adsorbing onto surfaces (which have computed adsorption energies around -7 eV), the most exothermic entry is $$\mathrm{I_{2}\ (g)} + 2* \rightarrow 2 \mathrm{I}^*$$ on a Pt(111) surface with a value of -3.49 eV with the SCAN functional. This definitely seems very exothermic to me.
• Is I_{2} meant to be $I_2$ ? – Nike Dattani Apr 30 '20 at 21:20