Electronic structure and charge compensation in Au_xAg_25-xSR₁₈¹⁻ (x = 0, 12, 13, 25), AuAg₁₂Au₁₂SR₁₈¹⁻, and AgAu₁₂Ag₁₂SR₁₈¹⁻ clusters

The stability and electronic properties of Au_xAg_25-xSR₁₈¹⁻ (x = 0, 12, 13, 25), AuAg₁₂Au₁₂SR₁₈¹⁻, and AgAu₁₂Ag₁₂SR₁₈¹⁻ clusters with aromatic and aliphatic ligand groups are investigated using density functional theory. We find differences in atomic geometries, energy gaps, and charge distributions, depending on the metal atoms in the outer shells composing staple units. Clusters with gold staple units show larger gaps than silver ones. The analysis of the total and partial density of states shows that HOMO and LUMO states are mainly from the inner shell metal atoms belonging to icosahedral structures, which characterize such clusters’ atomic arrangement. We also find that sulfur atoms in ligands linked to silver and gold capping units behave differently. In contrast to other known clusters, charge distributions of this cluster size are different, where a charge compensation is not present, allowing their synthesis with a plethora of ligands. These results confirm the use of ligands with different natures to obtain clusters of this particular size experimentally.