A semiempirical study of C₂₄N₄ and its boron-nitrogen analogs

The results of semiempirical calculations on the heterofullerence C₂₄N₄ and its boron-nitrogen analogs B₆N₁₀C₁₂ (the smallest CBN ball) are presented in accordance with considerations of chemical bondings and geometries. The structures and relative properties of the 28-atom cages, C₂₈, C₂₄N₄, and B₆N₁₀C₁₂, were investigated using semiempirical methods contained in the MOPAC program. C₂₄N₄ and B₆N₁₀C₁₂ have T_d and C₃ symmetry, respectively. B₆N₁₀C₁₂ has four geometric isomers, and their optimized structures were determined. The ionization energies, vibrational frequencies, IR intensities, and various thermodynamic properties (including entropy and heat capacity) for C₂₄N₄ and B₆N₁₀C₁₂ were calculated by the MNDO method. The evidence suggests that a B₆N₁₀C₁₂ cage is more stable than that of C₂₄N₄. Possible experimental methods to prepare B₆N₁₀C₁₂ are also proposed. © 1996 John Wiley & Sons, Inc.