Geometric structures, stability and properties of Mg₃Bn_n^0/- (n=1-8) clusters

The geometric structures, stabilities and properties of Mg₃B_n^0/-(n=1-8) clusters have been systematically investigated using the particle swarm optimization structure prediction program (CALYPSO) combined with density functional theory. The lowest energy structures were obtained at the single-point CCSD(T)/aug-cc-pvdz level based on the geometries optimized at the B3LYP/6-311+G(d) level. Mg₃B₃^- and Mg₃B₄^- were found to adopt 2D planar structures, whereas all the other clusters had 3D structures. The neutral and anionic clusters possess similar structures in the case of n=3, 6, and 8. Subsequent calculations of the average binding energies, secondorder energy differences, and HOMO-LUMO gaps indicate that theMg₃B₆ and Mg₃B₇^- clusters have the highest stability. The electronic properties of the clusters were further analyzed by calculating charge transfer and Wiberg bond orders. Based on the Multiwfn program, the photoelectron spectra, infrared spectra and Raman spectra were computationally simulated to facilitate their spectral characterization. Investigation of the thermodynamic properties showed that the heat capacity and entropy increase with increasing temperature and that the relationships between C_v(S) and T are approximately quadratic.