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难熔元素钨在NiAl位错体系中的占位及对键合性质的影响*
The site preference of refractory element W in NiAl dislocation core and its effects on bond characters*
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摘要: 用第一性原理离散变分方法研究了难熔元素钨(W)在金属间化合物NiAl?100?(010)刃型位错体系中的占位以及对键合性质的影响,计算了纯位错体系和掺杂体系的能量参数(结合能、杂质偏聚能及原子间相互作用能)、态密度和电荷密度分布.体系结合能和杂质偏聚能的计算结果表明:难熔元素W优先占据Al格位.此外,由于难熔元素W的4d轨道与近邻基体原子Ni的3d轨道和Al的3p轨道的杂化,使得掺杂体系中难熔元素W与近邻基体原子间的相互作用能加强;同时难熔元素W与位错芯区近邻基体原子间有较多的电荷聚集,这表明W与近邻基体原子间形成了较强的化学键.难熔元素W对NiAl化合物的能量及电子结构有较大的影响,从而影响位错的运动及NiAl金属间化合物的性能.Abstract: The site occupancy of refractory element W in the?100?(010) edge dislocations of NiAl intermetallic compounds and its effect on NiAl properties are studied by the first-principles discrete variational method. The energetic parameters (binding energy, the impurity segregation energy and the interatomic energy), the density of states and the charge density are calculated respectively for the clean dislocation system and the doped dislocation system. The calculated results of the binding energy and the impurity segregation energy suggest that W exhibits a strong Al site preference. The interactions between the refractory elements W and the neighbouring host atoms are strengthened due mainly to the hybridization of 4d orbital of impurity atom and 3d orbital of host Ni atoms (3p orbital of host Al atom). Meanwhile, some charge accumulations appear between impurity atom and neighbouring host atoms in the dislocation core, indicating that strong bonding states are formed between the impurity atom and its neighbouring host atoms. The refractory element W greatly affects the energy and the electronic structure of NiAl intermetallic compounds, and in turn influences the motion of dislocation and the properties of NiAl compound.
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