为了从微观结构层面揭示载荷条件下Cr、Mo掺杂合金钢与H原子的相互作用机制，本工作采用第一性原理的方法从位点空间构型、能量、电子结构、扩散能垒四个方面探究了Cr-Mo协同掺杂和ε对α-Fe中H占位及扩散的影响。结果表明，无论是否施加预应变(ε)，H原子均优先占据四面体位点而非八面体位点；在Cr-Mo协同掺杂体系中，H占据纯Fe位点时的结构稳定性高于占据Fe-Cr位点时，后者会导致显著的内聚能损失，加剧氢脆倾向，而Mo原子的引入有效减少了Cr周围可被H占据的Fe-Cr位点数量，从而抑制氢脆。施加预应变会降低晶体结合能(E_b)，且降幅与|ε|正相关，H的嵌入进一步降低E_b，但不改变E_b随ε变化的整体趋势。Cr-Mo协同掺杂破坏了晶格对称性，在预应变与H原子的共同作用下，各四面体位点的几何参数(金属与H间距及金属原子间的间距)、能量参数(结合能、溶解能)及电子结构参数(Bader电荷、积分晶体轨道Hamilton布居(ICOHP))均呈现各向异性，导致H在体相中的扩散行为表现出各向异性。此外，H倾向于从Fe-Cr位点向纯Fe位点扩散，反向过程则受阻；压缩预应变通过提高垂直于ε方向的扩散能垒，抑制外部H向内渗透及内部H在该方向的双向扩散，减少H进入高风险Fe-Cr位点的概率，从而缓解氢脆；而拉伸预应变则促使H在垂直于ε方向的平面富集，加速裂纹萌生与脆性断裂。

The mechanism of hydrogen embrittlement (HE) is highly sensitive to material composition, microstructure, local hydrogen concentration, hydrogen pressure, and loading conditions. Although experimental studies have consistently demonstrated that high-strength steels under tensile stress are susceptible to mechanical degradation from hydrogen uptake, the atomic-scale mechanisms underlying stress- and strain-induced HE remain unclear. Previous atomic-scale, first-principles investigations have primarily focused on two areas: (1) the role of individual alloying elements in modulating hydrogen diffusion in metallic systems; (2) the influence of prestrain (ε) on hydrogen diffusion in pure or homogeneous metals. However, first-principles studies that explicitly address the combined effects of ε, microstructural heterogeneity, and H are lacking. To elucidate the interaction between Cr–Mo alloyed steel and H under ε, we employ density functional theory for probing their tripartite interplay in α-Fe. Our analysis focuses on four critical aspects: site geometry, energetics, electronic structure, and diffusion barriers. Results show that H atoms consistently favor tetrahedral (T) sites over octahedral (O) sites, regardless of applied ε. In the Cr–Mo codoped system, H occupancy at pure Fe sites is energetically more favorable than at Fe–Cr sites. The latter induces substantial cohesive energy loss, thereby increasing HE susceptibility. Importantly, Mo incorporation considerably reduces the number of Fe–Cr sites accessible to H near Cr atoms, effectively mitigating HE. Application of ε lowers the crystal binding energy (E_b), with the magnitude of reduction scaling positively with |ε|. Hydrogen incorporation further reduces E_b but does not alter the overall ε-dependent trend. Cr–Mo codoping breaks the lattice symmetry. Under the combined effects of ε and H, T sites exhibit marked anisotropy in geometric parameters (metal—H and metal—metal distances), energetic descriptors (binding and solution energies), and electronic structure metrics (Bader charge and integrated crystal orbital Hamilton population). This anisotropy drives directionally dependent H diffusion in the bulk. In addition, H preferentially migrates from Fe–Cr sites toward pure Fe sites, whereas the reverse process is kinetically hindered. Compressive ε elevates the diffusion barrier for H migration perpendicular to the ε direction, thereby suppressing external H ingress and internal bidirectional diffusion along this path. This reduces the likelihood of H populating high-risk Fe–Cr sites and thus alleviates HE. In stark contrast, tensile ε promotes H accumulation in planes perpendicular to ε, accelerating crack nucleation and brittle fracture.