高压下ReB_(2)的结构特性及弹性性质

Structural Characteristic and Elastic Property of ReB_(2) under High Pressure

本文采用密度泛函理论中的赝势平面波法计算了ReB_(2)的P6_(3)/mmc晶体结构(即hP6-ReB_(2))的结构特性及弹性性质。在计算了hP6-ReB_(2)的平衡结构参数后,从热力学、动力学及机械力学三方面验证了其结构稳定性。研究发现,hP6-ReB_(2)在高压下的弹性系数、各个弹性模量均随压强的增加而增大。泊松比显示hP6-ReB_(2)表现为脆性。三种类型的弹性波随压强的变化趋势显示hP6-ReB_(2)为弹性各向异性晶体。经估算,hP6-ReB_(2)结构的维氏硬度约为38.2 GPa。电子态密度揭示了hP6-ReB_(2)的Re—B和B—B之间存在着强共价键,并且随着压强的增加共价键逐渐增强。

The structural characteristic and elastic property of ReB_(2) in P6_(3)/mmc structure(hP6-ReB_(2))were computed using the pseudopotential plane-wave methods based on the density functional theory.The equilibrium structural parameters of hP6-ReB_(2) were calculated and its stability was verified thermodynamically,dynamically,and mechanically.It is found that the elastic constants,aggregate moduli increase as the pressure increases,and the Poisson ratioσof hP6-ReB_(2)structure shows its brittleness,and the elastic waves reveals its elastic anisotropy.In addition,the obtained Vickers hardness of hP6-ReB_(2) is 38.2 GPa.The density of electronic states reveals that there is a strong covalent bond between Re-B and B-B of hP6-ReB_(2),and the covalent bond increases gradually with the increase of pressure.