Structure and electronic properties of Hn@C20 molecule

Density functional theory has been employed to optimize the structure of endohedral doped C20 fullerene. We have also investigated electronic properties. We have found that C20 cage can accommodate up to 8 hydrogen atoms. Some hydrogen atoms get chemisorbed on the inner surface of C20 cage and form C–H bond. Structural deformation is found to increase with increase in H-atoms. From the analysis of electronic properties, we observe that due to endohedral doping of hydrogen atoms inside C20, H-atoms acquire net negative charge by accepting electrons and fullerene molecules acquire positive charge by donating electrons to H-atoms. For endohedral complexes where H3 triangular molecule formation takes place, the nature of net charge transfer changes, i.e. fractional electronic charge is transferred from H-atoms to fullerene. C20 doped with odd number of H-atoms should be more reactive compared to the even number case. Most of the present results are similar to those of endohedral C60.

Research highlights
► C20 cage may accommodate up to 8 hydrogen atoms.
► For more than 8 hydrogen atoms, cage wall eventually breaks and binding energy changes drastically.
► H-atoms acquire net negative charge by accepting electrons and fullerene molecule acquires positive charge.
► For complexes where H3 triangular molecule formation takes place, the nature of charge transfer gets reversed.
► C20 doped with odd number of H-atoms should be more reactive compared to the even number case.