Temperature dependence of the spectral profile and total intensity of the second-harmonic signal of the fullerene crystal.

The temperature dependence of second-harmonic generation in crystalline fullerene is simulated based on a microscopic model of orientational disorder, with special emphasis on the vicinity of the phase transition. The temperature-induced changes of the total second-harmonic intensity and of the corresponding spectral profile are treated on equal footing within a consistent theoretical framework. In addition to the previously applied approach where superexchange-type exciton transfer via the charge transfer (CT) manifold was described phenomenologically, and alternative model invoking the CT states explicitly is proposed, giving deeper insight into the underlying physics. Both models yield very good agreement with experimental results.