C20−n Ge n heterofullerenes (n = 5–10) on focus: a density functional perspective

Abstract

We are focusing our calculations on the structural stabilities and electronic properties of six novel C20−n Ge n heterofullerenes, with n = 5–10, at B3LYP/6-311++G** and B3LYP/AUG-cc-pVTZ levels. Vibrational frequency calculations on C20 and its six C20−n Ge n analogs show them as true minima. In contrast to identical bonds in the former, contractions of C=C double bonds are encountered at the expense of longer C–Ge bonds in heterofullerenes. Band gaps (ΔE HOMO–LUMO) of heterofullerenes become narrower as n increases. As to band gaps, C14Ge6 immerges with the highest ΔE HOMO–LUMO = 1.81 eV. Hence, it is predicted to be most stable against electronic excitation. It has C i symmetry and contains four germanium atoms in equatorial and two at the cap positions. On the other hand, C15Ge5 appears with the lowest ΔE HOMO–LUMO = 1.25 eV. It has C 5v symmetry and contains five alternating germanium atoms in equatorial position. So, C15Ge5 is predicted to orchestrate a higher conductivity and charge transfer, making it a possible candidate for hydrogen storage. Assuming the binding energy (E b) as a criterion of stability, the more stable species turn out to be both C20 parent fullerene, and C15Ge5 heterofullerene with E b = 8.0, and 7.0 eV/atom, respectively.