ABSTRACT
In addition to the fact that chemical bonds between carbon atoms are strong, the fullerene molecule has a closed-shell electronic structure. us, when the fullerenes form a cluster, chemical bonds in the molecules do not play a signi cant role. e cohesive force between fullerenes is the van der Waals force. For systems interacting through such a force, the Lennard-Jones potential is o en used for describing the interaction. e potential V between two molecules can be written as a function of the distance r between the centers of the molecules:
LJ LJ LJ4 .V r r r
⎧ ⎫σ σ⎛ ⎞ ⎛ ⎞ = ε −⎨⎜ ⎟ ⎜ ⎟ ⎬⎝ ⎠ ⎝ ⎠⎩ ⎭ (37.1)
In this formalism, r0 = 21/6σLJ gives the equilibrium distance for a potential well depth of εLJ. Table 37.1 lists the values of the potential parameters σLJ and εLJ for various pairs of atoms and molecules. (As is discussed later, the potential between two C60 molecules is somewhat di erent from the Lennard-Jones potential. is table lists only the rough estimates of the equilibrium distance and well depth of a C60 dimer.) eir polarizability, α, dielectric constant, ε, and density, ρ, in the solid phase (almost at the boiling point) are also shown. e Clausius-Mossotti equation gives the relation between α, ε, and the number density ρn:
1 4 . 2 3 n
ε − π = ρ α
ε + (37.2)
From Table 37.1, we can draw the following inferences.
