Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Phys Chem Chem Phys. 2018 Sep 12;20(35):22762-22767. doi: 10.1039/c8cp04129f.
We identified by ab initio calculations a new simple orthorhombic carbon allotrope with Pmc21 (C2v2) symmetry that has a 32-atom unit cell in all-sp3 hybridized covalent bonds. This new carbon phase can be formed from graphite via a one-layer by three-layer slip and buckling mechanism along the [210] direction above 7.16 GPa and is more favorable than previously proposed cold-compressed graphite phases such as Z-carbon and M-carbon in terms of both kinetics and energetics. Its dynamic stability has been confirmed by phonon mode analysis. Electronic band structure calculations reveal that it has a large indirect band gap of 5.91 eV, wider than that of diamond, which is expected to be optically transparent. The calculated hardness of 95.1 GPa is comparable to 97.5 GPa for diamond. These results offer insights into understanding the complex structural landscape of compressed graphite.
我们通过从头算计算确定了一种具有 Pmc21（C2v2）对称的新的简单正交碳同素异形体，其具有全 sp3 杂化共价键的 32 原子单元胞。这种新的碳相可以通过一层到三层的滑移和屈曲机制从石墨中形成，沿着[210]方向在 7.16 GPa 以上，在动力学和能量学方面都优于以前提出的冷压缩石墨相，如 Z-碳和 M-碳。其动力学稳定性已通过声子模式分析得到证实。电子能带结构计算表明，它具有较大的间接带隙为 5.91 eV，宽于金刚石，预计具有光学透明性。计算得到的硬度为 95.1 GPa，与金刚石的 97.5 GPa 相当。这些结果为理解压缩石墨的复杂结构景观提供了新的见解。
