The effect of hydrogenation on the structure of Ru19 – has been studied using a combination of trapped ion electron diffraction and density functional computations. While the bare Ru19 – cluster has a closed-shell octahedral geometry, hydrogenation of the cluster changes the structure type of the ruthenium core toward an icosahedral motif. The experiments show a gradual structural transition depending on the number of adsorbed hydrogen atoms. Density functional theory computations reveal the driving force behind this process to be the larger hydrogen adsorption energies for the bi-icosahedral structure and predict a corresponding structural rearrangement at around 20 adsorbed hydrogen atoms, which is consistent with the experimental findings. Additionally, the computations provide insight into the hydrogen-binding situation. They show that hydrogen is preferentially atomically bound only to surface Ru atoms. H2 binding is predicted only at high hydrogen loadings.

The structures of platinum cluster anions Pt 6 − −Pt 13 − have been investigated by trapped ion electron diffraction. Structures were assigned by comparing experimental and simulated scattering functions using candidate structures obtained by density functional theory computations, including spin−orbit coupling. We find a structural evolution from planar structures (Pt 6 − , Pt 7 − ) and amorphous-like structures (Pt 7 − −Pt 9 − ) to structures based on distorted tetrahedra (Pt 9 − −Pt 11 − ). Finally, Pt 12 − and Pt 13− are based on hcp fragments. While the structural parameters are well described by density functional theory computations for all clusters studied, the predicted lowest energy structure is found in the experiment only for Pt 6 − . For larger clusters, higher energy isomers are necessary to obtain a fit to the scattering data.

We present a study of the structural effects of hydrogen adsorption on Ru14 – investigated by a combination of trapped ion electron diffraction and density functional computations. While the bare Ru14 – forms a double layer hexagonal structure, the adsorption of hydrogen initiates an evolution of the metal core toward an icosahedral structure. The structural rearrangement is driven by the difference in mean hydrogen adsorption energies, gradually stabilizing the icosahedral cluster core structure for higher hydrogen coverage. Detailed temperature dependent measurements reveal a crossover between the two structure motifs and indicate a structural phase equilibrium. Accompanying free energy computations confirm the chemical equilibrium and identify a hydrogen coverage instability region where the cluster hydrides decompose into the two core isomers with different hydrogen coverage.

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