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Deuterium uptake and sputtering of simultaneous lithiated, boronized, and oxidized carbon surfaces irradiated by low-energy deuterium

Summary

Molecular dynamics with ReaxFF potentials extended to treat B and Li on carbon surfaces quantifies D retention and sputtering yields for Li–C–B–O mixtures exposed to low-energy D, comparing selected results to new experiments on B–C–O–D systems to interpret how oxygen modulates fueling/recombination-relevant D behavior in plasma-facing carbon scenarios. The study is positioned as a composition-resolved complement to single-species carbon erosion benchmarks, emphasizing how mixed conditioning layers reorganize under sequential deuterium impact.

Methods

From the J. Appl. Phys. PDF (pdf_path); Sec. II gives the simulation recipe.

  • Potentials / code: ReaxFF for Li-B-C-O-D with EEM charges, implemented in LAMMPS. Li-B parameters trained vs NWChem PBE0/ 6-31G DFT (bond/angle/binding benchmarks in Fig. 1*).
  • Surface cell: ~400 atoms, lateral ~1.8 nm, depth ~2.0 nm (z); amorphous B/Li/C/O mixtures prepared by melt/quench + 300 K Langevin thermalization for each composition (Sec. II B).
  • D irradiation: Projectiles 5 eV (retention) and 5 eV / 30 eV (sputtering, as stated). Sequential bombardment: D launched 0.7 nm above the surface every 50 ps at random x,y; 20 ps NVE-like cascade evolution, 20 ps rethermalization to 300 K, 10 ps relaxation before the next impact (Sec. II B). Saturation preparation continues until D_acc plateaus (<0.5% change). Production statistics use N = 15000 independent impacts on a prepared surface (embarrassingly parallel as described).
  • Observables: Reported quantities connect time-accumulated retained deuterium, sputtered species yields, and surface composition evolution so that simulation outputs can be read alongside experimental surface-analysis channels discussed in the article.
  • Boundaries / pressure / timestep: 3D PBC on the amorphous slab cells as in Sec. II. Impact cycling alternates short NVE cascade segments with rethermalization toward 300 K; N/A — NPT barostat and N/A — imposed bulk pressure in the quoted bombardment workflow. Integration timestep values are given numerically in Sec. II of the Journal of Applied Physics PDF (pdf_path).

Findings

  • Oxygen participates strongly in D bonding pathways across the explored compositions; comparative experiment + simulation highlights mechanisms for D retention in B–Li–C–O mixtures relevant to conditioned PFC chemistry.
  • Boron can suppress carbon erosion relative to reference surfaces; lithium increases oxygen surface content under D bombardment in regimes discussed in the paper, modulating retention.
  • The study positions mixed conditioning (Li + B + O) as a knob for erosion vs retention trade-offs in fusion PFC applications.
  • Comparisons and sensitivity: Computational retention and sputtering metrics are read against new experiments on B–C–O–D surfaces and related datasets discussed in the article; trends depend on impact energy (5 eV versus 30 eV channels) and on B/Li/O composition of the prepared films.
  • Limitations / corpus: Classical ReaxFF omits explicit electronic sputtering; absolute yields should be taken from tables in the PDF rather than this wiki summary. Proof duplicate ingest: 2018dominguez-venue-paper.

Limitations

  • Classical reactive models omit electronic sputtering channels explicit in higher theory; energies focus on the low-energy experimental window emphasized in the article.
  • Surface heterogeneity in real tokamak tiles (roughness, mixed materials) exceeds the idealized flat B/Li/C/O mixtures simulated here, so absolute retention numbers should be extrapolated to devices only with experimental anchoring.

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