Theoretical study of the binding of Na clusters encapsulated in the fullerene

Density functional theory has been used to study the electronic structure and binding of (Formula presented) clusters (N≤30) encapsulated inside the large fullerene (Formula presented). One or more electrons are always transferred from the endohedral (Formula presented) to the cage. The charge density distribution reveals that for small N the binding between (Formula presented) and the fullerene is purely ionic, and that for N≳9 a covalent contribution to the bonding develops, enhanced by the expansion of the endohedral (Formula presented). The evolution of the type of bonding with increasing N is analyzed by comparing the size variations of the binding energy and the ionization potential of the (Formula presented) clusters. © 1996 The American Physical Society.

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