H1 = -0.16 eV/H. At high surface coverage, the most favorable configuration has all H sites filled and a doublevacancy in B sites (see Fig. ), ∆∆e (100) H8B14 = 0.40 eV/H. The minimum energy path from low to high coverage can go through the hollow-occupied quadrant (see Fig. ) or through the bridge-occupied quadrant (see Fig. ). The H6 adsorption energy, ∆∆e (100) H6 = 0.006 eV/H, is intermediate to that of the low and high coverage while the H2B16 energy, ∆∆e (100) H2B16 = 0.62 eV/H, exceeds that of the high coverage states. As a result, we expect that surface hydrogens fill H sites before starting to occupy B sites. Importantly, the adsorption energies of the random structures are bounded on the low end by the path CDF shown in Fig. (see also line CDF on Fig. ) and on the high end by the cluster of bridge-occupied structures (see point E on Fig. ). Up to surface coverages of θ ≈ 1/3, the lowest energy configurations only have occupied H sites and the adsorption energy is a weak function of coverage. At higher coverages, hydrogens have to occupy the higher energy B sites and the adsorption energy increases to approximately 0.4-0.5 eV/H, exceeding the 10 k B T threshold at θ ≈ 0.65.