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 C20-nGen 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 C-20 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 C-20, contractions of C=C double bonds are encountered at the expense of longer C?Ge bonds in C20-nGen. In contrast to previous reports on silicon doped heterofullerenes, none of the computed heterofullerenes collapses to open cage structures. Successive Ge doping on C-20 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.