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
The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order p...The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order phase transition has been reported.The activation energy change around 274 K and the lambda-like specific heat peak beginning at 270 K and ending at 310 K show that there is an orientational phase transition in fcc C60 crystals above 251 K.By taking the symmetry into consideration and further analyzing lambda-like specific heat peak and the activation energy change around 274 K,the conclusion has been reached that this new phase transition is an orientational structure transition from the merohedral twinning fcc to the orientationally disordered fcc.The temperature of free rotation of C60 molecules is about 281 K.展开更多
To investigate the deformation of a molecule in a crystal field or the intra-and intermolecular interaction of a molecular solid, one should study not only the position but also the orientation of a molecule. Since th...To investigate the deformation of a molecule in a crystal field or the intra-and intermolecular interaction of a molecular solid, one should study not only the position but also the orientation of a molecule. Since the structure of a C<sub>60</sub> molecule is a truncated icosahedron composed of 20 6-MRs （six-membered rings）and 12 5-MRs, its symmetry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Project supported by the National Natural Science Foundation of China.
文摘The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order phase transition has been reported.The activation energy change around 274 K and the lambda-like specific heat peak beginning at 270 K and ending at 310 K show that there is an orientational phase transition in fcc C60 crystals above 251 K.By taking the symmetry into consideration and further analyzing lambda-like specific heat peak and the activation energy change around 274 K,the conclusion has been reached that this new phase transition is an orientational structure transition from the merohedral twinning fcc to the orientationally disordered fcc.The temperature of free rotation of C60 molecules is about 281 K.
基金Project supported by the National Natural Science Foundation of China
文摘To investigate the deformation of a molecule in a crystal field or the intra-and intermolecular interaction of a molecular solid, one should study not only the position but also the orientation of a molecule. Since the structure of a C<sub>60</sub> molecule is a truncated icosahedron composed of 20 6-MRs （six-membered rings）and 12 5-MRs, its symmetry
