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利用密度泛函理论框架下的离散变分DV和DMol方法,根据单杂质固溶模型和结构缺陷复合模型,研究了微合金化元素Nb在铁γ相中的作用.分别计算了合金化元素Nb在晶体内、晶界和表面的杂质形成能,结果表明:与在体内占位相比,晶界更适合Nb元素占据.Nb在晶界和在表面上的杂质形成能之差为-0.39 eV<0,根据Rice—wang热力学模型可以判定,Nb在铁γ相中可增强晶界结合.原子间相互作用能和电荷密度计算表明,当Nb原子占据晶界位置时,Nb与周围的相互作用减弱,距Nb原子较近的跨晶界的基体原子间的相互作用加强,从而使得晶界迁移变得困难,在电子层次解释了Nb在铁γ相晶界上的拖拽作用.
The effect of micro-alloying element Nb on iron γ phase was studied by using discrete variational DV and DMol methods under the framework of density functional theory (DFT). According to the single-impurity solution model and structural defect model, the effects of alloying element Nb In the crystal, the grain boundary and the surface of the formation of impurities, the results show that: compared with occupying in the body, the grain boundary is more suitable for the occupation of Nb.Nb in the grain boundary and the formation of impurities on the surface of the difference is -0.39 eV < 0, according to the Rice-wang thermodynamic model, it can be determined that Nb can enhance the grain boundary bonding in the iron γ phase.The calculation of the intermolecular interaction energy and charge density shows that when the Nb atoms occupy the grain boundary position, the interaction between Nb and the surroundings is weakened , The interaction between the matrix atoms closer to the Nb atom in the intergranular boundary is strengthened, making the migration of the grain boundary difficult, and the drag effect of Nb on the γ-γ intergranular boundary is explained electronically.