Nonlinear optical susceptibilities of fullerenes in the condensed phase

We present results for nonlinear optical susceptibilities of fullerenes, in cluding C-60, C-70, and C-84, in the condensed phase from large-scale nb in itio calculations using self-consistent reaction field theory and an analyt ical local-field method. It is shown that the intermolecular polarization i nteraction has significant effects on the nonlinear properties of the fulle renes, and that, in some contrast to other organic species, nondipolar cont ributions to this interaction are important. Based on the theoretical and e xperimental results for the polarizability of C-60 in the gas phase, a gene ral local-field factor for C-60 film has been obtained, which is found to b e quite different from the classical Lorenz-Lorentz local-field factor. The calculated and experimental nonlinear optical susceptibilities of C-60 are in good agreement provided the comparison is made on the same basis, viz a t nonresonant frequencies and considering the relevant macroscopic quantiti es. The dielectric and density dependence of the nonlinear optical suscepti bilities of C-70 are discussed.