Effect of the off-diagonal disorder on second-harmonic generation intensity in C60

The influence of the rotational disorder in the high-temperature phase of C60 fullerene on the second-harmonic generation (SHG) intensity is studied on a cluster model of the crystal. The results are compared with the experimental data [A.M. Janner et al., Phys. Rev. B 52 (1995) 17158]. The off-diagonal disorder of the Frenkel exciton transfer integrals is identified as the main factor leading to the reduction of the SHG signal with increasing temperature.