How do atomic layers affect hydrogen adsorption energies on the Al(111) surface?

[Hanlin]

Hi.

I'm trying to calculate the adsorption energies at all high symmetry sites on an Aluminium (111) surface (consisting of a few atomic layers). The adsorbates are hydrogen atoms. I make sure that one hydrogen atom per primitive surface cell is adsorbed (i.e. one monolayer of hydrogen atoms is adsorbed onto the surface). Now I'd like to understand how the number of atomic layers (which are all perpendicular to the (111) direction) affect the adsorption energy: will it increase/decrease with an increasing number of atomic layers? Is it possible to understand this by plotting the charge density variations on the surface? I am using Dacapo/python by the way. If you have the answer, could you help me?

Best Regards

Someone who could really use your wisdom.

 

[Modey3]

Hanlin,

Have you ever tried plotting surface-energy vs. number of layers. If so you will find that for between 3-6 (depending on the system) that surface energy oscillates with number of layers. This is due to there being a higher fraction of occupied "surface-states" compared to the "bulk-states" My guess is that since surface-energy oscillates so does the absorption energy.

Best Regards

modey3