Probing the effects of lithium doping on structures, properties, and stabilities of magnesium cluster anions

Bimetallic clusters have aroused tremendous interest because the property changes like structure, size, and composition have occurred. Herein, a structural search of the global minimum for anionic ${\mathrm{LiMg}}_n^{-}$ (n = 2–11) clusters is performed using an efficient crystal structure analysis by particle swarm optimization (CALYPSO) structural searching program with subsequent density functional theory (DFT) calculations. A great variety of low energetic isomers are converged, and the most stable ones are confirmed by comparing their total energy of each size. It is found that the ${\mathrm{LiMg}}_n^{-}$ clusters are structurally consistent with corresponding Mg clusters anions except for ${\mathrm{LiMg}}_5^{-}$ and ${\mathrm{LiMg}}_7^{-}$. In all the doped clusters, the Li atom prefers to occupy the convex position. Simulated photoelectron spectra (PES), Infrared (IR), and Raman spectra of ${\mathrm{LiMg}}_n^{-}$ could be used as an essential evidence for identifying cluster structures experimentally in the future. Stability study reveals that a tower-like structure of ${\mathrm{LiMg}}_9^{-}$ has prominent stability and can be identified as a magic number cluster. The reason might be that there are both closed-shell 1S²1P⁶1D¹⁰2S² electronic configurations and stronger Li–Mg bonds caused by sp hybridization in the ${\mathrm{LiMg}}_9^{-}$ cluster.