Electronic structure and properties of rhombohedrally polymerized C60

Abstract

The valence electronic structure of rhombohedrally polymerized C60, synthesized at 6 GPa and 725 °C, has been studied using x-ray emission spectroscopy. The C Kα spectrum of the polymer was found to differ from that of the C60 fullerite especially in the high-energy region. The observed spectra were compared to densities of states, calculated using a tight-binding approximation for three two-dimensional hexagonal C60 networks, distinguished by the nature of intermolecular bonding. Theoretical spectra of the polymers agree well with experiment and indicate that changes in the valence band of C60 upon polymerization are mainly due to the formation of intermolecular bonds, and only to a negligible degree due to a distortion of the C60 cage. Rotation of C60 within the hexagonal layer changes dramatically the electronic properties of the polymer from a semiconducting behavior for the structure with 66/66 connections to a metallic behavior for a layer containing C60 molecules that are linked through 56/65 bonds. The occurrence of the latter configuration may explain the observed metalliclike in-plane conductivity of the rhombohedral phase of C60.

Well‐Defined Fullerene Nanowire Arrays

“…[25] The rhombohedral phase of the C 60 fullerene formed under high pressures and high temperature has been well studied. [18,19,26] The covalent bonding between C 60 molecules in the polymeric phase was found to play a primary role in determining the electronic structure and property of rhombohedrally polymerized C 60 . [18,19,27] Density functional (LDA) and tight-binding model calculations of the rhombohedral phase and its two-dimensional layer found the fundamental gap to be narrower and the band dispersion larger in comparison to bulk C 60 fullerite.…”

“…[18,19,26] The covalent bonding between C 60 molecules in the polymeric phase was found to play a primary role in determining the electronic structure and property of rhombohedrally polymerized C 60 . [18,19,27] Density functional (LDA) and tight-binding model calculations of the rhombohedral phase and its two-dimensional layer found the fundamental gap to be narrower and the band dispersion larger in comparison to bulk C 60 fullerite. [27] The semiconducting or semimetal properties of materials depend on the intermolecular connection pattern present in the layered or chained lattice.…”

Phase transformations in pressure polymerized C60

“…Polymerization of C 60 fullerene attracted considerable attention in part due to the promising properties of the resulting polymerized materials, e.g., their ferromagnetism, electrical conductivity, etc [1][2][3][4][5]. At present high temperature-high pressure treatment is the most advanced technique for polymerization of C 60 .…”

Low Band Gap and Ionic Bonding with Charge Transfer Threshold in the Polymeric Lithium Fulleride Li4C60

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Singly or doubly bonded dimers [1][2][3][4] and polymer chains, [5][6][7][8] as well as two-dimensional (2D) [9][10][11] and even three-dimensional [12][13][14] networks of C 60 molecules have been reported. The free energy of different structures is often very similar, resulting in an abundance of phase transitions which can be induced by temperature or pressure variations, light irradiation, or chemical doping as in alkali fullerides.…”