Empirical bond polarizability model for fullerenes

The static polarizability properties and the Raman-scattering intensities in molecular C₆₀ and C₇₀ are found to be well reproduced by a bond polarizability model with parameters similar to those obtained from studies of hydrocarbons. For the Raman spectrum of C₆₀ with off-resonance infrared laser excitation, a fit using first-principles vibrational eigenvectors yields α_∥^'-α_⊥^'=2.30 A², 2α_⊥^'+α_∥^'=2.30 A², α_∥-α_⊥=1.28 A³ for single bonds and α_∥^'-α_⊥^'=2.60 A², 2α_⊥^'+α_∥^'=7.55 A², α_∥-α_⊥=0.32 A³ for double bonds, with (α_∥-α_⊥) for the single bond arbitrarily set equal to its value in ethane, namely, 1.28 A³. The transferability of these parameters to C₇₀ is discussed in detail. {} 1996 The American Physical Society.