coverage determination

[apple]

hi,
I am looking at H adsorption on metal surfaces and I am interested in determining the max coverage for H on these surfaces. What is the best way of calculating it, i.e. should I look at how the binding energy per H changes as a function of H and when it achieves its most negative value, or should I look at how the energy changes with an addition of each extra H? In my system, the first approach favors 4 H adsorbed on the surface, while the second method shows that the adsorption of 5 H is fine. What's the best way of approaching this problem?
I would appreciate if someone could respond.

[tlchan]

You can calculate the formation energy of the structure. If there is energy release during the formation, the structure is theoretically possible. Note that your question may not be experimentally relevant. For a given coverage, the experiment may observe different unit cells that you haven't considered, the structure may start to grow 3-dimensionally or form domains with different coverage.