The melting of fullerites from small or large fullerenes

ISSN： 0018-151X

Source： High Temperature, Vol.45, Iss.3, 2007-06, pp. : 321-326

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Abstract

The physical limits are studied theoretically for a mass of fullerenes which may be used to produce a stable crystal, i.e., fullerite. The dependence of the parameters of interfullerene interaction on the mass of fullerene C_nc is used to study the evolution of the properties of fullerite as a result of variation of the number of carbon atoms nc in fullerene C_nc. The dependences of the energy of activation process and surface energy are calculated for different values of temperature and pressure in the 15 ≤ nc ≤ 147 range. It is demonstrated that fullerite becomes unstable at nc < 20, because small-sized light fullerenes cannot be localized due to weak Van der Waals forces. At the same time, fullerites with nc ≥ 110 exhibit abnormally low values of surface energy; this must bring about the fragmentation of nanoclusters of hollow spherical C_nc molecules of such a large size. Four empirical equations are used to estimate the dependence of the melting temperature of fullerite on nc. It is demonstrated that the melting temperature in the case of fullerites from small or large fullerenes is lower than that in the case of fullerites at 50 < nc < 90. It is inferred that the 30 < nc < 100 range is optimal for the formation of stable fullerite.