Structures And Stability Of Hydrogenated Carbon, Silicon And Germanium Clusters

Carbon fullerene and their derivatives have been studied extensively for their potential application value in electronic devices, hydrogen storage materials and other fields. Silicon and germanium clusters which located in the same main group as carbon also have been attracted people's attention because of their practical value in semiconductor devices.In this paper, the structures and stability of C₆₀H_n (n=2-20,24) have been studied at the level of density functional theory (DFT). The results showed that the most stable structures of C₆₀H_n (n=8-20,24) were originated from non-IPR C₆₀ clusters in addition to C₆₀H_n (n=2-6). For C₆₀H_n (n=10-20, 24), some structures originated from six non-IPR C₆₀ clusters were more stable than them originated from C₆₀/I_h. In these non-IPR C₆₀ clusters, theoretical calculations also found that when all of the bonds five-membered rings shared (N₅₅) were occupied by hydrogen atoms, the structures were more stable. HF and density functional theory (DFT) have been performed to investigate the structures and stability of Si₆₀H₆₀. Among all 1812 all-exo Si₆₀H₆₀ fullerene isomers, we found that the most stable iso- mer had a tube-like configuration (D_5d) with twelve five-membered rings fused and located at the ends of the tube. The most stable cage isomer could admit ten to twelve endo Si-H bonds (H₁₀@Si₆₀H₅₀ and H₁₂@Si₆₀H₄₈), and they also represented the most stable Si₆₀H₆₀ isomers. It was found that Si₆₀H₆₀ isomers had much lower angle and torsion strains than the corresponding C₆₀H₆₀ isomers.Density functional theory (DFT) calculations have been carried out on the structures and stability of Ge₆₀H₆₀. It was found that the tube-like Ge₆₀H₆₀/D_5d was more stable than the Ih cage isomer. Both cage- and tube-like Ge₆₀H₆₀ could admit same numbers of endo bonds as Si₆₀H₆₀. The most stable tube isomer could admit four to eight endo Ge-H bonds, and the most stable cage isomer could admit ten to twelve endo Ge-H bonds (H₁₀@Ge₆₀H₅₀ and H₁₂@Ge₆₀H₄₈ ). The most stable Ge₆₀H₆₀ was cage-like isomer with endo Ge-H bonds. It was found that Ge₆₀H₆₀ isomers had much lower angle and torsion strains than the corresponding Si₆₀H₆₀ isomers.