硫原子在镍基合金825(001)面吸附的第一性原理研究

元素硫在镍基合金表面吸附产生严重的电化学腐蚀,为从原子尺度研究硫腐蚀机理,采用第一性原理方法,构建并优化了镍基合金825的晶胞结构模型,计算分析了S原子在镍基合金825耐蚀性较差面(001)晶面的吸附及电子转移情况.结果表明:Ni原子占据顶角, Cr原子和Fe原子对称占据面心是镍基合金825稳定的晶胞结构;原子S在镍基合金825(001)面上最稳定的吸附位为四重穴位,吸附能为-6.51 eV; S吸附前后的态密度(DOS)和二维电荷差分密度图(DCD)对比发现,镍基合金825中Fe与S之间电荷偏移明显,形成离子键,易生成腐蚀产物Fe_xS_y. S的吸附对镍基合金825中Cr原子的电子分布影响不大,且合金中Cr和Ni抑制了合金中Fe与S之间的相互作用,从而提高了合金耐蚀性.

First-Principle study of S adsorption on nickel-based alloy 825 (001) surface

Density Functional Theory(DFT) was used to build and optimize the 825 alloy cell model, and atomic S adsorption on 825 alloy (001) surface was calculated and analyzed. The results show that the model in which the Ni atoms occupy the apex corner, the Cr atoms and the Fe atoms symmetrically occupy the face center is the most stable unit cell structure of 825 alloy;The most stable site of atomic S adsorption on the 825 alloy (001) surface is the H site with the adsorption energy of 6.84eV; The density of states and two-dimensional differential charge density map can fully prove that the charge transfer between Fe and S in nickel-based alloy 825 is obvious, forming an ionic bond, which may generate corrosion products FexSy; The adsorption of S has little effect on the electron distribution of Cr atoms in the alloy, compared with pure Fe, the interaction between S and Fe in nickel-based alloy 825 is obviously weakened,Cr is a key additive element for the corrosion resistance of Alloy 825.