點(diǎn)缺陷對(duì)B2-CoSc化合物物性影響的第一性原理研究

點(diǎn)缺陷對(duì)B2-CoSc化合物物性影響的第一性原理研究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軟件，對(duì)B2型金屬間化合物CoSc的16種點(diǎn)缺陷的熱力學(xué)參數(shù)、電子結(jié)構(gòu)和彈性常數(shù)進(jìn)行計(jì)算，分析16種點(diǎn)缺陷存在的類(lèi)型及對(duì)化合物力學(xué)性能的影響。結(jié)果表明：Co單空位形成熱和結(jié)合能分別是-6.78 eV和-0.43 eV，Co單空位化合物最容易形成、穩(wěn)定性最好；其次是Co單反位化合物，形成熱和結(jié)合能分別是-6.152 eV和2.504 eV。從而得出16種點(diǎn)缺陷最穩(wěn)定存在形式是Co空位和Co反位；存在的組態(tài)是Co單空位、Co雙空位、Co三空位和Co雙反位。由電子態(tài)密度圖中的費(fèi)米能級(jí)和贗能隙也定性判斷出，Co空位和反位缺陷化合物比Sc空位和反位缺陷化合物穩(wěn)定。計(jì)算6種點(diǎn)缺陷的泊松比 可知， Co三空位的化合物金屬鍵最強(qiáng)、塑性最好。與完整的CoSc金屬間化合物塑性相比，有空位缺陷的金屬間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-CoSc 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 eV and -0.43 eV, respectively, so the B2-CoSc 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 eV and 2.504 eV, 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 CoSc 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 CoSc intermetallic.

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