V, Mn, Mg在α-Fe(N)中占位及电子结构的第一性原理研究

A First Principle Study on Occupancy and Electronic Structure of V, Mn, Mg in α-Fe(N)

氮(N)是冶炼不锈钢的重要合金化元素,具有强烈的奥氏体化能力,对于生产节镍型不锈钢而言, N不可或缺,但在常规冶炼工艺中,很难实现向钢中高效、经济的增N。基于第一性原理方法探讨了增氮过程中合金元素M(M=V, Mn和Mg)对N稳定性的影响,采用VASP软件计算了M(M=V, Mn和Mg)掺杂α-Fe(N)体系的择优占位、结合能、态密度及电荷密度。计算结果表明, V和Mg优先固溶在晶胞的顶角位置, Mn优先固溶在晶胞的体心位置。V的掺杂加强了晶胞的稳定性, Mn的掺杂略微降低晶胞的稳定性, Mg的掺杂显著降低晶胞的稳定性。V, Mn在α-Fe晶胞中均存在金属键和离子键的共同作用,成键轨道主要来自M 3d, Fe 4s 3p 3d与N 2p。当N掺杂在α-Fe体系的八面体间隙后,金属原子失去电子, N得到电子, V的掺杂显著加强了N与周围金属的相互作用, Mn与Mg的掺杂对周围Fe与N的作用相对不明显。

Nitrogen(N) is an important alloying element for smelting stainless steel and has a strong austenitizing ability. For the production of nickel-saving stainless steel, N is indispensable. But in the conventional smelting process, it is difficult to achieve high efficiency and economic increase of N in steel. Based on the first-principles method, the effects of alloying elements M(M=V, Mn and Mg) on the stability of N were investigated. The preferred occupancy, binding energy, density of states and charge density of M doped in α-Fe(N) system were calculated by VASP software. The results showed that V and Mg were occupied preferentially the corner of α-Fe(N) unit cell, Mn was occupied preferentially the body-centered position of the cell. The doped element V was strengthened the stability of α-Fe(N), Mn had an opposite effect, however, Mg was disadvantageous for the structural stability of α-Fe(N). The metallic and the ionic bonds were coexisted in the doped systems except for Mg. The bonding orbitals were created by the interaction of M 3 d, Fe 4 s 3 p 3 d and N 2 p. Doped metal atoms lost electron, N got electron. Doped of V in α-Fe(N) was strengthened the interaction between N and the surrounding metals, but the interaction was unremarkable for the other doped metals.