Density Functional Theory Study of Structural, Electronic and Optical Properties of 13-Atom Au-Ag-Cu Ternary Clusters

The structural, electronic, and optical properties of 13-atom Au-Ag-Cu ternary clusters are systematically investigated using density functional theory (DFT). The results indicate that the structural configurations of Ag_11-nCu₂Au_n (n = 2, 3, 4, 5, 6, 7, 9), Ag_10-nCu₃Au_n (n = 3, 4, 6, 7, 8, 9), Ag_8-nCu₅Au_n (n = 4, 5, 6, 7), Ag_11-nCu₁Au_n (n = 8, 9), Ag_7-nCu₆Au_n (n = 5, 6), and Ag_6-nCu₇Au_n (n = 3, 5) clusters exhibit irregular structural configurations, while other ternary clusters exhibit icosahedral-like geometries. In terms of stability, Ag₉Cu₂Au₂, Ag₇Cu₂Au₄, Ag₅Cu₂Au₆, Ag₃Cu₇Au₃, Ag₃Cu₃Au₇, Ag₁Cu₉Au₃, Ag₁Cu₆Au₆, and Ag₁Cu₃Au₉ clusters are identified as more stable than their neighboring clusters, based on the excess energy and second-order difference energy. Regarding the electronic properties, all ternary clusters exhibit reduced HOMO-LUMO gaps compared to pure clusters. Notably, the Ag₁Cu₇Au₅ cluster shows the highest ionization potential and the lowest electron affinity, whereas the Ag₈Cu₃Au₂ cluster displays the opposite trend. Regarding the optical properties, most 13-atom Au-Ag-Cu ternary clusters demonstrate a red shift relative to pure clusters, with absorption spanning from the visible to the near-UV region. Of the Au-Ag-Cu ternary clusters investigated here, the Ag₆Cu₁Au₆ cluster exhibits the strongest absorption peak at 314.70 nm, whereas the Ag₅Cu₃Au₅ cluster shows the strongest absorption in the visible region. This study identified significant factors affecting the stability of Au-Ag-Cu ternary clusters, providing direction for future research on the stability of more complex ternary clusters. Investigation of optical properties offers a theoretical basis for the prospects of Au-Ag-Cu ternary clusters as optoelectronic materials.