Endohedrally doping the gold cage [formula omitted] with an trivalent atom B, Al, Ga, and In: Density functional studies

Abstract

The relativistic density functional calculations explore that M@Au16- (M=B, Al, Ga, and In) with M at the cage center, named as M@Au16--center, should be the most stable. The M@Au16--center (M=B, Al, Ga, and In) clusters have closed-shell electronic structures and large energy gaps. All of these properties are characteristic of a magic cluster and can be well understood by the jellium model. Therefore, we strongly suggest M@Au16--center (M=B, Al, Ga, and In) are magic clusters and promising as building blocks in developing cluster-assembled materials. The energy levels and the wavefunctions of frontier orbitals explore that the HOMOs of M@Au16--center should be partly occupied by the M atom, while the LUMOs of them should be mostly from the Au16- bodies. The difference charge densities and the natural bonding orbital charge analyses imply the Au–M bonds have both the ionic and covalent characters. Finally, the mean static linear polarizabilities and first-order hyperpolarizabilities of M@Au16--center are larger than those of Au16-, while their anisotropies of the polarizability tensors are smaller than those of Au16-. We rationalize the nonlinear properties by studying the low-energy optical absorption band obtained by employing time-dependent density functional theory.