Following a number of studies, fluxional metal clusters are described here as Boltzmann ensembles at temperatures typical for thermal dehydrogenation (700 K). All the Pt 4 Ge x (x = 0-4) cluster structures predicted to be populated are shown in Fig. , and the most relevant minima are shown in Fig. . Several distinct isomers within 0.4 eV from global minimum (GM) for each composition were found, except for Pt 4 Ge, for which a single isomer is predicted to dominate the population. Note that the ensemble spread is not a monotonic or oscillating function of the Ge content. Pt and Ge exhibit strong mixing, similar to PtSn and PtSi supported cluster alloys. As found in previous works, Ge doping quenches the unpaired electronic spins of Pt, by forming polar covalent Pt-Ge bonds, again analogously to Sn and Si. In Pt 4 , > 90% of the population possesses unpaired electrons, while all the bimetallic clusters have a closed-shell electronic structure. To gain insight into the stability of PtGe cluster structures, a phase diagram as a function of the chemical potential of Ge (μ Ge ) is built based on the ensemble-average of all thermally accessible isomers at 700 K. The chemical potentials of Ge in bulk germanium, GeCl 4 (precursor used to prepare PtGe/Al 2 O 3 through ALD-like process) , and GeO 2 are used as references to calculate the ensemble-averaged formation energies. Pure Pt 4 is favored over a wide range of μ Ge . Pt 4 Ge becomes a more accessible composition as μ Ge becomes larger, and this composition was indeed observed in recent experiments where GeCl 4 was used as a precursor. Pt 4 Ge 4 should be experimentally accessible under Ge-rich conditions, possibly using a different precursor or a laser ablation preparation method. A narrow region of Pt 4 Ge 3 accessibility is also observed, and Pt 4 Ge 2 is also not far in stability in the same window of μ Ge (Figure , right). For comparison, the GM-based phase diagram is depicted in Fig. using dashed lines. Considering the ensemble of thermally populated isomers or only the most stable cluster structure does not have a large influence in the relative stability of the PtGe nanoclusters and stoichiometry accessibility, although it has a great impact in the catalytic properties, as it will be shown below. Note that poorly-accessible stoichiometries might suffer disproportionation via sintering over time. However, these results also indicate that a variety of stoichiometries could be accessible dynamically in catalytic conditions, especially under the influence of adsorbates. Catalytic effects may be governed by the minority species, and thus, properties of all stoichiometries are worth considering.