I am doing adsorption calculations on different surfaces of a metal using DFT, calculating work functions and adsorption energies. Is it Possible that a certain surface of a metal has higher work function as compare to other surfaces but certain elements are adsorbed easily on the same high work function surface as compared to other surfaces. I have attached the picture for a reference to look. the adsorption energy shows easier adsorption as compare to other surfaces, but the same surface has the highest work function as compare to other surfaces. I will be really thankful, if someone can explain it.
1) The work function is dependent on the surface orientation, so an orientation-dependent variation is normal.
2) Different surface orientations provide multiple different adsorption sites, each of which has a characteristic energy.
How good chemisorption happens, depends
scenario A: on the relative energies of conduction band and adsorbate HOMO -> bond is formed by electron transfer from the adsorbate to the surface
scenario B: on the relative energies of valence band and adsorbate LUMO ->bond is formed by electron transfer from the surface to the adsorbate
So, of course the work function plays a role here, but since the match of orbital/band pairs is the central quantity here, you will probably observe a trend for most metals, but there is no explicit law stating "high work function=low adsorption energy" or vice versa.
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