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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?

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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.

Anyway, for what you're actually asking, -10 eV sounds far too exothermic. It is almost certainly unreasonable. Perhaps your surface structure rearranged upon adsorption, there is some algebra error, some settings were changed, or a spin state was not correctly accounted for.

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  • $\begingroup$ Is I_{2} meant to be $I_2$ ? $\endgroup$ – Nike Dattani Apr 30 '20 at 21:20
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    $\begingroup$ Yup, adjusted now. $\endgroup$ – Andrew Rosen Apr 30 '20 at 21:22
  • $\begingroup$ What about the * for the 2? $\endgroup$ – Nike Dattani Apr 30 '20 at 21:24
  • $\begingroup$ No, that should not be superscripted because it's considered a species. It should be superscript on the I^* though to indicate the phase. IMO. $\endgroup$ – Andrew Rosen Apr 30 '20 at 21:24
  • $\begingroup$ Okay, I was just asking, because the original version had a superscript :) $\endgroup$ – Nike Dattani Apr 30 '20 at 21:25

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