A reactive force field approach to modeling corrosion of NiCr alloys in molten FLiNaK salts
Summary¶
Arkoub, Dwivedi, van Duin, and Jin present an Applied Surface Science article (DOI 10.1016/j.apsusc.2024.159627) that develops a ReaxFF description for Ni–Cr alloys interacting with multicomponent molten fluorides, focusing on FLiNaK-class salts relevant to molten salt reactor technologies. The motivation is compatibility: Ni-based structural alloys are candidate materials for high-temperature fluoride circuits, yet corrosion—often involving Cr depletion and interfacial speciation—is difficult to probe in situ at liquid salt interfaces. By fitting ReaxFF to first-principles data for F interactions with metal surfaces and molten salt bonding motifs, the authors aim to make atomistic reactive MD a complement to electrochemical and gravimetric tests, supplying mechanistic hypotheses about dissolution pathways and electrical double layer structure that continuum models rarely resolve.
Methods¶
ReaxFF training (A)¶
DFT targets: Ni, Cr, Li/Na/K/F EOS/reactions for FLiNaK-relevant stoichiometries.
Alloy–melt reactive MD (B)¶
Ni–Cr slabs + molten fluoride melts (NVT-style per keywords); RDFs/structure vs experiment/literature; Li fraction sweeps for EDL/speciation vs Cr release—Δt, T, duration in papers/Arkoub_Dwivedi_FLiNaK_salts_AppSurfSci_2024.pdf.
Electrode–electrolyte observables. The simulations emphasize interfacial Cr release as a function of melt composition and electrical double layer structure, comparing radial distribution functions for F⁻/Li⁺ layering near Ni/Cr terminations with literature expectations for molten fluoride salts. Readers should copy alloy compositions (Ni/Cr ratio), surface facet, melt stoichiometry, and thermostat settings from the Methods section when reproducing reported trends.
MD application (alloy, molten FLiNaK). LAMMPS+ReaxFF on Ni–Cr slabs wetted by FLiNaK melt cells—NVT as in Appl. Surf. Sci. 2024 (keywords); N/A for untranscribed atom counts, 3D PBC/slab vacuum thickness, time step (fs), Nosé–Hoover/Berendsen thermostat parameters, and ps/ns equilibration/production segments—see papers/Arkoub_Dwivedi_FLiNaK_salts_AppSurfSci_2024.pdf. N/A—NPT barostat if isobaric control is not used. Melt temperature is the operating window given in the article. N/A—macroscopic external electric field; N/A—umbrella; Hydrostatic stress in NPT segments N/A unless the paper used NPT—per full text.
Findings¶
The authors report that ReaxFF simulations capture Cr dissolution behavior consistent with fluoride-mediated corrosion phenomenology and strong sensitivity to both alloy composition and melt chemistry. A highlighted mechanistic motif is that higher Li content can promote a more compact electrical double layer at the interface, which mitigates Cr dissolution in the modeled scenarios—linking electrostatic interfacial structure to macroscopic corrosion propensity within the force-field approximation. The paper positions these atomistic pathways as especially valuable where experimental access to reactive interface chemistry is limited, while stressing that absolute rates and long-time kinetics must be interpreted with ReaxFF uncertainties inherited from training coverage and DFT reference choices. Corrosion stakeholders should pair these MD insights with continuum mass-transport and electrode polarization models when extrapolating to engineering lifing, because atomistic segments rarely span hours of real time or macroscopic crevice geometries. FLiNaK composition shifts (e.g., impurity halides, oxide carryover) remain an operational variable that any single parameter sweep in the article only partially samples.
Relevance to group¶
ReaxFF deployment for nuclear molten-salt materials compatibility with Ni-based alloys—application-forward extension of reactive metal/halide chemistry.
Citations and evidence anchors¶
- DOI:
10.1016/j.apsusc.2024.159627