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本文利用第一原理离散变分方法,计算了轻杂质P、N在体心Fe∑3[110](111)晶界和Fe(111)表面的偏聚能,从能量方面对P,N的韧脆机制进行了探讨。结果表明,P在晶界上的偏聚能比表面上更高,更有利于偏聚在表面而非晶界,而N则相反。因此,P为脆性杂质,N为韧性杂质,此结果与实验观察相符。还分析了造成这一结果的化学因素和力学因素的影响,指出了在计算中对原子结构进行弛豫的必要性
In this paper, the first principle of discrete variational method is used to calculate the partial energy of light impurity P, N on the bulk FeΣ3 [110] (111) grain boundaries and Fe (111) Ductile mechanism was discussed. The results show that the segregation energy of P at the grain boundaries is higher than that of the surface, which is more favorable for segregation on the surface but not on the grain boundaries, while N is the opposite. Therefore, P is a brittle impurity, N is a ductile impurity, and the result agrees with the experimental observation. The effects of chemical and mechanical factors that have contributed to this result are also analyzed, pointing out the need for relaxation of the atomic structure in the calculations