Hydrogen effects on the generalized stacking fault energy in α -Fe: a comparative atomistic simulation study

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Abstract Understanding the influence of hydrogen on slip resistance in crystals is essential for elucidating the microscopic mechanisms of hydrogen-enhanced local plasticity and hydrogen embrittlement. As a key physical quantity characterizing slip resistance, the accurate evaluation of the generalized stacking fault energy (GSFE) is of critical importance. However, there is currently no consensus on the appropriate methodology for GSFE calculations in hydrogen-containing systems, leading to significant discrepancies among existing studies. To address this issue, we perform systematic atomistic simulations to calculate the GSFE curves of the slip system in body-centered cubic α -Fe. Different methodological choices in two key steps (i.e. shearing and relaxation) of GSFE calculations are compared. For hydrogen-containing systems, an incremental shear and full relaxation of hydrogen atoms are more reasonable for GSFE calculation. Based on this validated approach, the effect of hydrogen spatial distribution on GSFE is further investigated. The results reveal a pronounced position dependence of GSFE on hydrogen position: hydrogen atoms located at tetrahedral interstitial sites on the slip plane significantly reduce the unstable stacking fault energy, thereby lowering the barriers for slip, whereas hydrogen atoms away from the slip plane may increase slip resistance. Moreover, a complex coupling effect on the GSFE emerges when hydrogen atoms are distributed on and away from the slip plane. This work systematically evaluates GSFE calculation strategies for hydrogen-containing systems and elucidates the position-dependent mechanisms by which hydrogen modulates GSFE, providing a reliable methodological reference for atomistic simulations under hydrogen environments.

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