New Phases of C ₆₀ Synthesized at High Pressure

Abstract

The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked.

Energetics of carbon peapods: Elliptical deformation of nanotubes and aggregation of encapsulatedC60

“…[7][8][9] The results indicate that the polymerization of C 60 takes place inside the nanotubes. It is well known that high pressure treatment under elevated temperature [31][32][33] and photoirradiation 34,35 for the solid C 60 results in the formation of polymeric phases of C 60 . Here, we have explored how nanotubes affect the energetics of C 60 polymerization.…”

Pressure-induced phase in tetragonal two-dimensional polymericC60

“…[1][2][3][4] Later new phases of polymerized fullerites have been synthesized starting from the pristine C 60 material by the use of highpressure and high-temperature treatment. [5][6][7] The various crystal structures of the polymers have been identified clearly as one-dimensional orthorhombic, 6 two-dimensional tetragonal, 6 and two-dimensional rhombohedral phases. 5,6 The polymerization is attained by the so-called ͓2ϩ2͔ cycloaddition mechanism via the formation of the fourmembered rings between adjacent fullerene molecules.…”

“…[5][6][7] The various crystal structures of the polymers have been identified clearly as one-dimensional orthorhombic, 6 two-dimensional tetragonal, 6 and two-dimensional rhombohedral phases. 5,6 The polymerization is attained by the so-called ͓2ϩ2͔ cycloaddition mechanism via the formation of the fourmembered rings between adjacent fullerene molecules. 8,9 The most interesting results are those which led to the threedimensional polymerization of fullerite, 10,11 a first stage to the synthesis of ultrahard phases.…”

Polymeric fullerene oxide films produced by decomposition of hexanitro[60]fullerene

“…To take advantage of the unique properties of the molecule and explore its potential applications as an optoelectronic material, quite a few research groups have attempted to prepare fullerenes into polymer and thin film forms [9,10]. Several approaches for the preparation of fullerene oligomers and polymers as carbon-based solids were reported in some prior studies, including photochemical [11], thermal [12], high pressure [13], plasma [14], thermobaric [15], and electro-induced methods [16]. Photoinduced polymerization of solid C 60 to form a polyfullerene film is known to follow a [2 + 2] condensation mechanism.…”