Probing the structural evolution, electronic and vibrational properties of neutral and anionic calcium-doped magnesium clusters

Metallic clusters have received tremendous interest due to the unusual structure and bonding along with potential as the motif for novel nanomaterials. Herein, the global minimum structures of neutral and anionic Mg-n(0/-) and CaMgn0/- (n = 2-15) clusters have been searched by utilizing the CALYPSO program with subsequent DFT calculations. For each cluster size, a large number of stable structures were converged, and then, the most stable ones were identified in light of the PES spectra and total energies. The results show that the most stable structures transform from planar to three-dimensional geometry at n = 3 and the hollow framework at n = 8, then to filled cage-like structure at n = 13. For all CaMgn0/- clusters, the Ca atom prefers to occupy the external capped site. The simulated PES, IR, and Raman spectra could provide additional ways to identify the structure of these clusters in the following experiments. In the range of studied size, a tower-like CaMg9 cluster is uncovered and proved to be a magic number cluster with superior stability. Analysis of charge transfer, molecular orbitals, multi-center bonds, and ELF reveals that the CaMg9 has 20 valence electrons of closed-shell 1S(2)1P(6)1D(10)2S(2) and more strong Ca-Mg bonds caused by spd hybridization.