第一性原理研究铱金属的致脆机理

First-principles Study on the Embrittlement Mechanisms of Iridium Metal

采用基于密度泛函理论的第一性原理方法对铱金属的致脆机理进行了研究。建立了Ir、Cu、Au、Si的晶胞模型,计算分析其电子结构、能带结构、力学性质等。根据金属塑性经验判据G/B比较得出,Cu和Au的塑性都非常好,而同样为面心立方金属的Ir却有着和非金属Si相似的脆性。分析电子结构发现,Cu和Au的电子云为均匀的圆球形,呈各向同性,这有利于原子间相互运动,从而有利于金属的塑性变形。Ir和Si的电子云有着相似的"花瓣状",极化严重,方向性明显;Ir原子间存在"伪共价"结构,这都对金属塑性变形产生了极大的阻力。能带结构和态密度的分析得出,Ir、Si相对于Cu和Au有着非常高的键强,这都不利于其塑性变形。因此,Ir的本征特点决定了其高的室温脆性。

The embrittlement mechanisms of iridium metal were studied based on first-principles density functional theory method.The electronic structure,band structure and mechanical properties of Ir,Cu,Au,Si lattice were calculated.According to metal plasticity experience criterion G/B,Cu and Au perform a good plasticity.But Ir with the face-centered cubic has the same plastic as non-metallic Si.It was found that Cu and Au have a circle electron cloud and isotropic with the analysis of electronic structure of this materials.It was useful to the movement of atoms and the plastic deformation of the metal.Ir and Si have a similar petal-like electron cloud with serious polarization and clear direction.Ir atoms generated a great deal of resistance to plastic deformation due to their pseudo-covalent structure.Analyses on the band structure and density of states demonstrated that Ir and Si possess very strong bond strength,which impairs plastic deformation.So it was determined the ductility at room temperature for Ir intrinsic characteristics.