Characterization of C20 fullerene and its isolated C20-nGen derivatives (n = 1-5) by alternating germanium atom(s) in equatorial position: A DFT survey

DFT calculations are applied to compare and contrast germanium atom(s) substituted C_20-nGe_n heterofullerenes with n = 1-5, where the substitution is completely isolated from each other by means of one carbon atom in equatorial position. The structural stabilities, geometry, and electronic properties of C₂₀ and its heterofullerene derivatives are compared and contrasted at M062X/6-311++G**, B3LYP/AUG-cc-pVTZ, B3LYP/6-311++G**, B3LYP/6-311+G*, and B3PW91/6-311++G** levels of theory. Vibrational frequency analysis shows that all of the heterofullerenes are real minima. Contrary to identical bonds in C₂₀, contractions of C=C double bonds are encountered at the expense of longer C―Ge bonds in C_20-nGe_n. In contrast to previous reports on silicon doped heterofullerenes, none of the computed heterofullerenes collapses to open cage structures. Successive Ge doping on C₂₀ induces more positive atomic charge on Ge atoms and more negative charge on C atoms. High charge transfer on the surfaces of our stable heterofullerenes provokes further investigations on their possible application for hydrogen storage. As to band gap, binding energy, heat of atomization per carbon, nucleus-independent chemical shift, aromaticity, and the smallest vibrational frequency C₁₉Ge immerges with the highest value. The reactivity in terms of ionization potential, nucleophilicity, electrophilicity, hardness, softness, maximum electronic charge, and proton affinity issues predicts C₁₉Ge as the most stable heterofullerene against electronic excitation.