Molecular Structures of Alumina Nanoballs and Nanotubes: A Theoretical Study

Molecular structures of alumina nanoballs and nanotubes have been determined. Tetrahedral, octahedral, and icosahedral alumina nanostructures were derived from Platonic solids and Archimedean polyhedra and were optimized by quantum chemical methods. I_h-symmetric balls, resembling their isovalence electronic analogues, fullerenes, are preferred. The nanoballs consist of adjacent Al₅O₅ and Al₆O₆ rings, similar to C₅- and C₆-rings of fullerenes. The structural characteristics of alumina nanoballs are dominated by π-electron donation from oxygen to aluminum. Alumina nanotubes can be derived from icosahedral nanoballs. The tubes alternate between D_5d- and D_5h-symmetries and are capped by halves of the icosahedral balls.