= -2.67 eV, consistent with previous results. We now sequentially fill the H and B sites on the (100) surface and compute ∆∆e (100) i for each configuration. We quantify how hydrogen adsorption changes as a function of surface coverage by computing an adsorption energy grid, whereby H and B sites are monotonically populated with hydrogens. In doing so, we can determine the energetic requirements for surface monolayer coverage. Fig. shows the per atom adsorption energies ∆∆e We can identify the most favorable configurations at low and high surface coverage and trace the thermodynamic minimum energy path between them. At low surface coverage, the most favorable adsorption occurs at an isolated hollow site (see Fig. ), ∆∆e