Mao Wendy L, Mao Ho-kwang, Eng Peter J, Trainor Thomas P, Newville Matthew, Kao Chi-chang, Heinz Dion L, Shu Jinfu, Meng Yue, Hemley Russell J
Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA.
Science. 2003 Oct 17;302(5644):425-7. doi: 10.1126/science.1089713.
Compressed under ambient temperature, graphite undergoes a transition at approximately 17 gigapascals. The near K-edge spectroscopy of carbon using synchrotron x-ray inelastic scattering reveals that half of the pi-bonds between graphite layers convert to sigma-bonds, whereas the other half remain as pi-bonds in the high-pressure form. The x-ray diffraction pattern of the high-pressure form is consistent with a distorted graphite structure in which bridging carbon atoms between graphite layers pair and form sigma-bonds, whereas the nonbridging carbon atoms remain unpaired with pi-bonds. The high-pressure form is superhard, capable of indenting cubic-diamond single crystals.
在室温下压缩时，石墨在约17吉帕斯卡的压力下会发生转变。利用同步加速器X射线非弹性散射对碳进行的近K边光谱分析表明，石墨层间一半的π键会转变为σ键，而另一半则以π键的形式保留在高压形态中。高压形态的X射线衍射图谱与一种扭曲的石墨结构一致，在这种结构中，石墨层间的桥连碳原子配对并形成σ键，而非桥连碳原子则通过π键保持未配对状态。这种高压形态是超硬的，能够压入立方金刚石单晶。
