点缺陷对B2-CoSc化合物物性影响的第一性原理研究

Effect of point defects on physical and mechanical properties of B2-CoSc intermetallic studied by first-principles method

利用第一性原理的Castep软件,对B2型金属间化合物Co Sc的16种点缺陷的热力学参数、电子结构和弹性常数进行计算,分析16种点缺陷存在的类型及对化合物力学性能的影响。结果表明:Co单空位形成热和结合能分别是-6.78 e V和-0.43 e V,Co单空位化合物最容易形成、稳定性最好;其次是Co单反位化合物,形成热和结合能分别是-6.152 e V和2.504 e V。从而得出16种点缺陷最稳定存在形式是Co空位和Co反位;存在的组态是Co单空位、Co双空位、Co三空位和Co双反位。由电子态密度图中的费米能级和赝能隙也定性判断出,Co空位和反位缺陷化合物比Sc空位和反位缺陷化合物稳定。计算6种点缺陷的泊松比?可知,Co三空位的化合物金属键最强、塑性最好。与完整的Co Sc金属间化合物塑性相比,有空位缺陷的金属间化合物塑性得到提高。

First-principles based on the density functional theory was conducted to systematacially investigate the thermodynamic parameters,the electronic structures and the elastic properties of B2-Co Sc intermetallic with 16 different point defects.Structural stability and elastic-plastic deformation mechanism were studied based on the calculation.The results show that the lowest formation heat and formation energy of single vacancy at Co site are-6.78 e V and-0.43 e V,respectively,so the B2-Co Sc intermetallic with single vacancy at Co site is the easiest to form at stead state at room temperature condition.The formation heat and the formation energy of anti-site defect at Co site are-6.152 e V and 2.504 e V,respectively,and the intermetallic with anti-site defect at Co site is also easier to form and more stable.It is concluded that the most possible forms of point defects are vacancy and anti-site defects at Co site.Specifically,they are single vacancy,double vacancies,three vacancies and double anti-site defects at Co site.The vacancy and anti-site defects at Co site are more stable than vacancy and anti-site defects at Sc site,followed by fermi level and pseudogap of electronic state density figure.Therefore,three vacancies defect at Co site of Co Sc intermetallic has the strongest metallic bonding and the best plasticity among the intermetallics with six kinds of point defects by comparing the values of poisson ?.So,the plasticity of intermetallics with vacancy defectes is improved,comparing with the plasticity of perfect Co Sc intermetallic.