Role of ligand type on the geometric and electronic properties of Ag–Au bimetallic clusters

The interactions of a set of typical ligands (–CN, –COOH, –CH3, –OH, –SH, –NH3, –NO, –NO2, N(CH3)2, and –PH3) with 13-atom icosahedral Ag–Au bimetallic clusters have been investigated by density functional theory (DFT) calculations. For the adsorption of all the ligands on the Ag13 cluster, the adsorption strength follows the order of Ag13–CN > Ag13–SH > Ag13–OH > Ag13–COOH > Ag13–CH3 > Ag13–NO2 > Ag13–N(CH3)2 > Ag13–NO > Ag13–PH3 > Ag13–NH3. Considering the composition effect, the adsorption strength of the ligands (X = –CN, –COOH, –CH3, and –NO2) on these clusters follows the order of Ag12Au–X > Ag13–X > Au12Ag–X > Au13–X. It is also found that the adsorption of the ligands (–NO, –N(CH3)2, and –PH3) on the Au-rich clusters can modify their geometric properties, and even the icosahedral structure of Au-rich clusters has been transformed into the more stable truncated octahedral one upon adsorption. Our results show that the geometric and electronic properties of Ag–Au bimetallic clusters can be tuned by the ligand type, which can provide useful insights for the preparation of ligand-stabilized Ag–Au bimetallic clusters by chemical reduction.