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Recently we developed a reactor chamber for the secure handling of radioactive materials. Using the arc discharge method for fullerene synthesis we could test the carbon encapsulation capability of uranium. The samples obtained, characterized by bulk and direct observation methods, show that uranium encapsulates as a dicarbide with two types of carbon covers: graphene sheets parallel to the external...
Data from recent experimental studies of C 60 under high pressures are collected and analyzed, concentrating on the polymerized states where covalent intermolecular bonds have been formed through treatment of molecular C 60 at high pressures and temperatures at or above room temperature. We give an overview of the observed phase transformations and the structures of metastable...
We discuss the structural and dynamic properties of C 60 polymerized under low-P, low-T conditions, and suggest that the disordered mixed orthorhombic-tetragonal-rhombohedral phases produced under these conditions arise from nucleation of molecular chains in random directions because of the quasi-free molecular rotation under standard reaction conditions in the fcc phase of C 60 ....
We have applied a density-functional based nonorthogonal tight-binding (DF–TB) method to study the structure, energetics and vibrational properties of different [C 60 ] n oligomers, n=2,3,4. We determine the stable equilibrium configurations and present Raman intensities for their vibrations within a bond polarization model, which allow the identification of various oligomer species...
Possibility of direct detection of doping atoms in C 60 solid clusters by high-resolution electron microscopy (HREM) was investigated by using calculated residual indices (R HREM ) and difference images. HREM images of C 60 doped with nitrogen and rubidium atoms were calculated as functions of accelerating voltage of microscope, crystal thickness and...
Four crystalline phases have been identified by TEM-analysis of C 70 -samples after high-pressure-high-temperature (HPHT) treatment. All the phases are triclinic and exhibit distorted fcc lattices with a doubled c 0 -parameter. Decrease of lattice parameters and increased density are explained by a two-stage process: dimerisation at the first stage and the formation of chains...
Samples of the hexagonal close-packed phase (h.c.p.) of fullerite C 60 with a low (less then 7%) content of more stable face-centered cubic (f.c.c.) phase were synthesized using cryoextraction with n-hexane. X-Ray diffraction analysis and thermogravimetry were applied for characterization of the samples. The role of n-hexane in the formation of the h.c.p. structure is discussed.
X-ray diffraction and Raman spectroscopy have been used to characterize the structures obtained when C 60 single crystals are treated at 2GPa–700K. Two different experimental procedures have been applied: the temperature is raised before the pressure is applied, or the opposite. The “heating-then-pressing” path leads to the tetragonal polymer structure (P4 2 /mmc) together with a minor...
Stability of the hcp modification of fullerite C 60 under heating, compression, and mechanical grinding was studied. It was established that uniaxial load and mechanical grinding caused transition of the hcp modification into more stable fcc modification, while no transition was observed upon heating or hydrostatic pressure. The results were discussed in terms of the theory of the deformation...
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