Compton Profiles and Electronic Density in C60

High-resolution measurements of Compton profile on C60 powder have been carried out as a function of temperature both below and above the orientational ordering phase transition (260 K). Simultaneously, theoretical profiles are obtained using the plane-wave expansion of wave functions from an ab initio self-consistent field calculation (SCF) of the energy band structure, using the linear combination of atomic orbitals (LCAO) method within the local-density approximation. Compared to graphite, the C60 profiles indicate substantially greater delocalisation of the ground-state charge density. We have demonstrated, both by experiment and calculation, that this delocalisation is mainly a molecular effect.