新型超硬材料z-BC2N的弹性、硬度与热导率研究

采用第一性原理计算研究了超硬材料z-BC₂N的弹性各向异性性质、应力-应变关系、硬度及最小热导率性质。计算得到的晶体力学行为判据B/G为0.87, 泊松比为0.084, 普适弹性各向异性指数为0.09992。100]晶向上最大拉伸强度达到180 GPa, 应变方向上最大剪切强度达到160 GPa, 维氏硬度值为77.07 GPa。基于Cahill模型得到的最小热导率为6.811 W/(m·K)。结果表明: z-BC₂N是脆性材料且力学稳定性良好, 有非常高的拉伸强度、剪切强度, 体弹模量为各向同性, 杨氏模量各向异性程度不大。z-BC₂N的最小热导率低于金刚石的最小热导率。

Investigation of Elastic Properties,Hardness and Thermal Conductivity of New Superhard Material z-BC2N

Based on the first-principles calculations, the elastic anisotropic properties, stress-strain relationship, hardness and minimum thermal conductivity of the superhard material z-BC₂N were investigated. Results show that the Pugh criterion B/G is 0.87, Poisson ratio is 0.084, and the universal elastic anisotropy index AU equals to 0.09992. The ultimate tensile strength along 100] crystal orientation is up to 180 GPa while the shear intensity ofdirection peaks at 160 GPa, and 77.07 GPa for the Vickers hardness of z-BC₂N. Based on Cahill model the calculated minimum thermal conductivity is 6.811 W/(m·K). Those data indicate that z-BC₂N belongs to brittle material with excellent mechanical properties such as the outstanding tensile strength and shear intensity, its bulk modulus is exactly isotropic and the Young's modulus witnesses a significant trend to be isotropic. Besides, z-BC₂N possesses a lower minimum thermal conductivity compared with diamond.