Optical and magnetic properties of Cu-doped 13-atom Ag nanoclusters

• Cu atom tends to occupy the core position in the Ag–Cu nanoclusters.
• Global minimum of Ag12Cu1 cluster is predicted to be cuboctahedral shape.
• High symmetry clusters have high magnetic moment.
• Icosahedral core–shell Ag12Cu1 cluster has ferromagnetic properties.

The structural, optical and magnetic properties of Ag13, Ag12Cu1 and Cu13 clusters have been investigated using density functional theory calculations. The global minimum of the Ag12Cu1 cluster is predicted to be cuboctahedral (COh) core–shell structure with Oh point group symmetry while the icosahedral (Ih) core–shell isomer has a higher HOMO–LUMO gap and higher magnetic moment. The optical absorption spectrum of the Ih Ag12Cu1 has three absorption peaks at 2.17, 2.41 and 2.65 eV, compared with that the COh Ag12Cu1 has one main absorption peak at 2.51 eV. The characteristics in electronic density of states (DOSs) show that Ih core–shell Ag12Cu1 has ferromagnetic properties like pure Au13, Ag13 nanoclusters. The sizable split between spin up and spin down DOS of d states in the inner Cu atom and sp states in the outer Ag atoms bring in large magnetic moment to Ih Ag12Cu1 cluster.