Structure and Stability of Tube and Cage Ge₆₀H₆₀

A tube Ge₆₀H₆₀ isomer in D_5d symmetry with fused five-membered rings located at the ends of the tube is more stable than the fullerene-like I_h cage isomer at the B3LYP/cc-pVDZ level of theory. Introducing endo Ge−H bonds increases the stability of both cage and tube isomers. The most stable tube isomer can admit six endo Ge−H bonds. The cage isomer can admit 10−12 endo Ge−H bonds (H₁₀@Ge₆₀H₅₀ and H₁₂@Ge₆₀H₄₈), and they also represent the most stable Ge₆₀H₆₀ isomers. The stability order and structural patterns of Ge₆₀H₆₀ are the same as those found for the corresponding Si₆₀H₆₀ isomers. Moreover, it is found that the 6-31G(d,p) basis set fails to predict the relative energies of the Ge₆₀H₆₀ isomers and the Ge₆H₆ isomers.