A calculation study on the configuration of Al12C clusters

The energetics and electronic structures of several Al12C configurations are calculated by a molecular orbital DMol3 program based on the density functional theory, and their configuration evolution are also investigated by means of the minimum energy path (MEP) with the aid of the climbing image nudged elastic band method (CI-NEB). A new low symmetrical isomer of Al12C clusters, i.e., Cs–Al12C, at a local minimum in the MEPs is detected. Several parameters, such as the binding energy Eb, the HOMO–LUMO energy gap ΔEH–L,ΔEH–L, the electron affinity EEA and the vertical electron detachment energy EVDE are adopted to characterize and evaluate the stability of Al12C configurations. The C atom in Cs–Al12C configuration is demonstrated to locate at the upside of a surface consisting of four Al atoms and some covalent bonds exist between the C and its four Al neighbors. The difference in Eb between Cs–Al12C and Ih–Al12C configurations is proved to be very small. Different from Ih icosahedron, the calculated EEA and EVDE of neutral Cs–Al12C configuration and the absorption spectra of anionic Cs–Al12C clusters are in good agreement with experimental data. The configuration evolution from neutral Cs–Al12C to neutral Ih–Al12C and the synthesis preference in the mode of Al12 + C → Al12C reveal Cs–Al12C configuration can coexist with the ground-state Ih–Al12C structure in energetics and Cs–Al12C configuration has a high formation ability compared with Ih–Al12C structure.