Electronic interactions in two-dimensional polymers of the C60 fullerene

Abstract

The electronic structure of tetragonal and rhombohedral polymers of the C60 fullerene is investigated using x-ray emission spectroscopy. It is found that, compared to the C60 molecular crystals, the formation of intermolecular covalent bonds in two-dimensional layers of the C60 fullerene polymers leads to a broadening of the maxima in the CK α x-ray emission spectra, a decrease in the density of high-energy states, and an increase in the width of the valence band of the polymer. The experimental data are interpreted by analyzing the results of the calculations performed within the density functional theory for the C60 fullerene cage forming eight and twelve covalent bonds. It is shown that the electronic interactions between C60 molecules in the polymerized layers are provided by two types of molecular orbitals located at energies 0.5–3.0 and ∼5.0 eV below the energy of the Fermi level.