Shi Zhijun, Shao Wei, Rao Lixiang, Xing Xiaolei, Zhou Yefei, Ren Xuejun, Yang Qingxiang
State Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, P. R. China.
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. China.
Phys Chem Chem Phys. 2022 Feb 23;24(8):5171-5184. doi: 10.1039/d1cp05163f.
A tetragonal CN (t-CN) structure was predicted CALYPSO code, and the effects of pressure on its structural and mechanical properties were studied. The results show that t-CN is different from various 2D CN compounds with a new type 3D crystal structure, which is similar to diamond. Bulk t-CN is equipped with excellent elastic properties. When the pressure is increased from 0 GPa to 350 GPa, its bulk modulus , shear modulus and Young's modulus are increased from 426.9 GPa to 1123.1 GPa, 371.4 GPa to 582.9 GPa and 863.7 GPa to 1490.9 GPa, respectively. The anisotropic , and are increased from 582.38 GPa to 1751.41 GPa, 478.29 GPa to 1033.97 GPa and 1281.26 GPa to 2490.14 GPa, respectively. When the pressure is 0 GPa, the hardness calculated by Chen's and Tian's models are 51.15 GPa and 51.81 GPa, respectively. Its ideal tensile strength in [111] orientation is the smallest (63.46 GPa), which indicates that the (111) planes allow easy cleavage. The smallest ideal shear strength (67.98 GPa) can be obtained in the (111)[11̄0] orientation, which suggests its theoretical hardness is about 67.98 GPa. Due to its excellent mechanical properties, t-CN can be used as an industrial superhard material.
利用CALYPSO程序预测了一种四方相的类金刚石结构（t-CN），并研究了压力对其结构和力学性能的影响。结果表明，t-CN具有不同于各种二维类金刚石化合物的新型三维晶体结构，与金刚石相似。块状t-CN具有优异的弹性性能。当压力从0 GPa增加到350 GPa时，其体模量、剪切模量和杨氏模量分别从426.9 GPa增加到1123.1 GPa、从371.4 GPa增加到582.9 GPa、从863.7 GPa增加到1490.9 GPa。各向异性的、和分别从582.38 GPa增加到1751.41 GPa、从478.29 GPa增加到1033.97 GPa、从1281.26 GPa增加到2490.14 GPa。当压力为0 GPa时，根据陈模型和田模型计算得到的硬度分别为51.15 GPa和5,181 GPa。其在[111]方向上的理想拉伸强度最小（63.46 GPa），这表明（111）面易于解理。在（111）[11̄0]方向上可获得最小的理想剪切强度（67.98 GPa），这表明其理论硬度约为67.98 GPa。由于其优异的力学性能，t-CN可作为一种工业超硬材料。
