Effect of Cu-doped site and charge on the optical and magnetic properties of 55-atom Ag cluster: A density functional theory study

In this study, the structures and magnetic properties of Cu single-doped Ag clusters are investigated by density functional theory (DFT). The optical spectrum of their neutral and charged states (−1, +1) are then examined by improved time-dependent DFT. Results show that Cu-doped site and charge affects not only structural stability of Ag55 cluster but also its performances. Icosahedral Ag54Cu1center cluster with Ih is more stable than icosahedral Ag54Cu1middle and Ag54Cu1sur clusters with Cs about 0.792 and 0.480 eV, respectively. Some prominent surface plasmonic resonance (SPR) peaks are observed in the absorption spectrum of these clusters particularly in the infrared region. Cu doping Ag55 cluster causes redshifts in the adsorption spectrum of Ag54Cu1middle (charged (−1) and neutral) and Ag54Cu1center clusters and blueshift in the adsorption spectrum of Ag54Cu1middle (charged (+1)) and Ag54Cu1sur cluster. The redshifts of SPR as well appear as a cluster changes from Ag55 to Ag54Cu1middle to Ag54Cu1center to Cu55 for the same charge. The Cu doping site has no effect on the magnetic properties of neutral clusters. However, Cu doped in the cluster center and with charge (+1) enhances the magnetic properties of the clusters four times compared with neutral clusters. Cu atom-doped and charge can tune physical and chemical properties of nanostructures and thus have many potential applications, especially in solar cells and sensors.