Nonlinear optical properties of the substituted fullerenes ${\mathrm{C}}_{59}$X (X=B,N)

Using the extended Su-Schrieffer-Heeger model and the sum-over-state method, we have calculated the third-order nonlinear polarizability γ and its dispersion spectra for single substituted fullerenes ${\mathrm{C}}_{59}$X (X=B or N atoms). Obtained results indicate that the substitute doping increases rather heavily the γ value, both the static and the dynamical response peak values. For ${\mathrm{C}}_{59}$N, the highest peak value of γ (at 3ω∼0.96 eV) is found to be about 30 times larger than that for pure ${\mathrm{C}}_{60}$, which may be important for its practical use.