Polymerization of C60 is realized under high temperature and high pressure. X-ray diffraction reveals a rhombohedral lattice structure in the product, and solid-state ^13C nuclear magnetic resonance spectroscopy confi...Polymerization of C60 is realized under high temperature and high pressure. X-ray diffraction reveals a rhombohedral lattice structure in the product, and solid-state ^13C nuclear magnetic resonance spectroscopy confirms the formation of sp^3 bonds between C60 molecules. Specific heat is then measured over the temperature range of 300-2 K. It is found that its specific heat values are significantly less than those in fullerite within the region of 80-2K, and this huge reduction is attributed to the suppression of intermolecular librational modes in polymerized C60. An excellent fit to the experimental data over the entire temperature range is provided by a model, which needs to include only three-dimensional and two-dimensional translational modes in various contributions at different temperatures.展开更多
Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impuri...Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impurities had been carefully excluded.This is attributed to phase transformation facilitated by nucleation around stacking faults.This proposal is supported by internal friction measurements on films,which confirmed the presence of this secondary transition,and by x-ray diffraction,which detected an hcp structure within the fcc lattice of C_(60) at room temperature.展开更多
基金Supported by the National Basic Research Programme of China under Grant No 2006CB705600, the National Natural Science Foundation of China under Grant No 10674060, the Natural Science Foundation of Jiangsu Province under Grant No BK2006109, the Doctoral Programme in Higher Education, and Baptist University of Hong Kong （FRG/05-06/I-52）.
文摘Polymerization of C60 is realized under high temperature and high pressure. X-ray diffraction reveals a rhombohedral lattice structure in the product, and solid-state ^13C nuclear magnetic resonance spectroscopy confirms the formation of sp^3 bonds between C60 molecules. Specific heat is then measured over the temperature range of 300-2 K. It is found that its specific heat values are significantly less than those in fullerite within the region of 80-2K, and this huge reduction is attributed to the suppression of intermolecular librational modes in polymerized C60. An excellent fit to the experimental data over the entire temperature range is provided by a model, which needs to include only three-dimensional and two-dimensional translational modes in various contributions at different temperatures.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grand No.BK97224Hong Kong Baptist University.
文摘Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders,not in single crystals,of C_(60) from which solvents and impurities had been carefully excluded.This is attributed to phase transformation facilitated by nucleation around stacking faults.This proposal is supported by internal friction measurements on films,which confirmed the presence of this secondary transition,and by x-ray diffraction,which detected an hcp structure within the fcc lattice of C_(60) at room temperature.
