Structural, optical, electronic, and magnetic properties of Ag-Cu bimetallic clusters: a density functional theory study

In this study, the structural, optical, electronic, and magnetic properties of Ag_mCu_n (m + n = 3 to 6) bimetallic clusters were systematically investigated by density functional theory in the theoretical framework of the generalized gradient approximation exchange-correlation functional. The results show that the ground state structures of these clusters are planar structures, with triangular geometries for three-atom Ag-Cu clusters, rhombic geometries for four-atom Ag-Cu clusters, trapezoids for five-atom Ag-Cu clusters, and triangular geometries for six-atom Ag-Cu clusters. The Ag₂Cu₂, Ag₂Cu₃, and Ag₃Cu₃ clusters are the geometric magic clusters for four-, five-, and six-atom Ag-Cu clusters, respectively. As the number of Cu atoms increases, the vertical ionization potential values of the four- to six-atom Ag-Cu clusters increase, while the vertical electron affinity values of the three- to five-atom Ag-Cu clusters decrease. Compared to pure Ag clusters, the main absorption peaks of the Ag-Cu clusters of the same number of atoms appear to blueshift. The even-numbered clusters exhibit no magnetic moments, while the odd-numbered clusters exhibit large magnetic moments of 1.00 μ_B. The magnetic moments of these Ag-Cu clusters are believed to be related to the atom sites.