On the stability of endohedral rare gas fullerenes

The stability of HeC60 and NeC60 is discussed in the context of a spherical model where the carbon atoms are smeared out into a uniform shell. The electronic properties of the 60 π-electrons together with those of the central atom are treated in the Thomas-Fermi approximation. Simple electrostatic reasoning elucidates the nature of the radial stability of the complex. A method to include nonspherical corrections is outlined. Possible bonding topologies of the central atom and the C60 cage are discussed, as well as the relevance of these topologies to incipient central atom distortions.