Nonlinear optical properties of Aun−mMm (M = Ag, Cu; m = 1, 2) clusters

Pure Aun (n = 10, 16) and their alloyed clusters Aun−mMm (M = Ag, Cu; m = 1, 2) are theoretically investigated for the structural characteristics, electronic properties, and nonlinear optical properties using density-functional theory (DFT) at B3LYP/LanL2DZ level. Doping exhibits little effect on structural characteristics and energy gaps but enormous augmenting of the second-order nonlinear optical (NLO) coefficients. The primary causation of the enhancement of β is the lack of centro-symmetry feature in alloyed clusters. Time-dependent density-functional theory (TD-DFT) analysis at the same basis set show doping increases the ground to excited state transition electric dipole moments and transition dipoles, which make important roles in enhancing the second-order NLO coefficients. Increasing number of M atoms increases the NLO coefficients of clusters because the M atoms act as electron donors in alloyed clusters. Increasing the length of clusters can also augment the β values in our investigation. The reported effect can be utilized to design effective gold-based alloyed clusters for NLO applications.