Grain boundary-specific effects of Mn concentration on hydrogen trapping and embrittlement in bcc Fe: A spin-polarised DFT study
Abstract
Hydrogen-enhanced decohesion at ferritic grain boundaries is controlled by the thermodynamics of hydrogen insertion, segregation, and interfacial cohesion. Here, spin-polarised density functional theory is used to examine how manganese concentration and site occupancy modify these quantities at two bcc Fe grain boundaries: the open Σ5(013)[100] (Σ5) boundary and the compact Σ3(1–12)[110] (Σ3) coherent twin. At Σ5, increasing manganese coverage produces a coverage-dependent reversal in hydrogen energetics: subsurface (low coverage) manganese weakens the intrinsic trap, combined core–subsurface (intermediate) occupation strengthens hydrogen stabilisation, and full decoration makes hydrogen insertion thermodynamically unfavourable. At Σ3, manganese consistently raises hydrogen solution and segregation energies, suppressing the already weak trapping tendency. At Σ5, magnetic sensitivity is observed only when manganese occupies boundary-core sites; subsurface manganese configurations are effectively spin-insensitive. Work-of-separation calculations show that manganese increases intrinsic cohesion and partially restores cohesion in hydrogen-containing Σ5 configurations. Charge-density-difference and Bader-charge analyses support the interpretation that manganese modifies local electronic redistribution around hydrogen, changing whether the boundary behaves as a deep trap or a passivated interface. Within the present ideal-cleavage, 0 K framework, manganese effects are governed by boundary geometry, concentration, and site occupation.
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BibTeX
@article{raj2026grain,
title = {{Grain boundary-specific effects of Mn concentration on hydrogen trapping and embrittlement in bcc Fe: A spin-polarised DFT study}},
author = {Ravi Raj and Drew Evans and Nikki Stanford and Isabelle Braems},
journal = {Materials \& Design},
year = {2026},
month = sep,
doi = {10.1016/j.matdes.2026.117047},
url = {https://hal.science/hal-05752861v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Grain boundary-specific effects of Mn concentration on hydrogen trapping and embrittlement in bcc Fe: A spin-polarised DFT study
AU - Ravi Raj
AU - Drew Evans
AU - Nikki Stanford
AU - Isabelle Braems
PY - 2026
DA - 2026/09/15
JO - Materials & Design
DO - 10.1016/j.matdes.2026.117047
UR - https://hal.science/hal-05752861v1
AB - Hydrogen-enhanced decohesion at ferritic grain boundaries is controlled by the thermodynamics of hydrogen insertion, segregation, and interfacial cohesion. Here, spin-polarised density functional theory is used to examine how manganese concentration and site occupancy modify these quantities at two bcc Fe grain boundaries: the open Σ5(013)[100] (Σ5) boundary and the compact Σ3(1–12)[110] (Σ3) coherent twin. At Σ5, increasing manganese coverage produces a coverage-dependent reversal in hydrogen energetics: subsurface (low coverage) manganese weakens the intrinsic trap, combined core–subsurface (intermediate) occupation strengthens hydrogen stabilisation, and full decoration makes hydrogen insertion thermodynamically unfavourable. At Σ3, manganese consistently raises hydrogen solution and segregation energies, suppressing the already weak trapping tendency. At Σ5, magnetic sensitivity is observed only when manganese occupies boundary-core sites; subsurface manganese configurations are effectively spin-insensitive. Work-of-separation calculations show that manganese increases intrinsic cohesion and partially restores cohesion in hydrogen-containing Σ5 configurations. Charge-density-difference and Bader-charge analyses support the interpretation that manganese modifies local electronic redistribution around hydrogen, changing whether the boundary behaves as a deep trap or a passivated interface. Within the present ideal-cleavage, 0 K framework, manganese effects are governed by boundary geometry, concentration, and site occupation.
SN - 0261-3069
SN - 0264-1275
ER -