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 AgmCun (m + n = 3 to 6) bimetallic clusters were systematically investigated by density functional theory in the theoretical framework of the generalized gradient approximation exchangecorrelation 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 oddnumbered clusters exhibit large magnetic moments of 1.00 mu(B). The magnetic moments of these Ag-Cu clusters are believed to be related to the atom sites.