The atomistic mechanism of chloride-induced depassivation of iron is still debated. A recent study suggests a four-stage depassivation mechanism, in general agreement with the point defect model. The proposed four-stage mechanism is based on reactive force field molecular dynamics simulations and is rather complex but here we use density functional theory to confirm the thermodynamic feasibility of the proposed mechanism. We find that the four surface species, formed in the four stages, have decreasing surface stability, which is consistent with the order of species formed in the depassivation process proposed in the reactive force field molecular dynamics study. The Fe vacancy formation energy, that is the energy needed to form a surface Fe vacancy by removing different surface species, indicates that surface species with more chlorides dissolve more easily from the surface, suggesting that chloride acts as catalyst in the iron dissolution process. The results are consistent with the suggested four-stage reaction mechanism and the point defect model.

氯化物诱导的铁钝化的原子机理仍存在争议。最近的一项研究提出了一种与阶段缺陷模型基本一致的四阶段钝化机制。所提出的四阶段机理基于反作用力场分子动力学模拟，并且相当复杂，但是在这里我们使用密度泛函理论来确认所提出机理的热力学可行性。我们发现，在四个阶段中形成的四个表面物种具有降低的表面稳定性，这与在反作用力场分子动力学研究中提出的去钝化过程中形成的物种的顺序一致。铁空位形成能，即通过去除不同的表面物种形成表面铁空位所需的能量，表明具有更多氯化物的表面物质更易于从表面溶解，表明氯化物在铁溶解过程中起催化剂的作用。结果与建议的四阶段反应机理和点缺陷模型相符。