Abstract
The departure from perfect spherical symmetry in the case of fullerenes (C60 being the sole exception) induces instabilities due to the stresses generated by the pentagonal protrusions in the σ-bonded surfaces. By assuming σ-π separability and treating π electrons as a degenerate Fermi gas in the two shells around the central σ structure, the resulting degeneracy pressures can further enhance the σ-surface initiated instabilities for non-icosahedral structures (especially for those <C60) as well as the icosahedral fullerenes (>C60) with large protrusions. Under certain circumstances the net degeneracy pressure across the σ surface may have a structure stabilizing effect. The role of the π-electron degeneracy in a broad range of fullerenes from C20 to C1500 and its effects on fullerene stability are investigated.