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Oxidation of nickel surfaces through the energetic impacts of oxygen molecules: Reactive molecular dynamics simulations

Summary

This slug is a duplicate PDF ingest for the Journal of Chemical Physics article DOI 10.1063/1.4945421 (volume 144, article 144705, 2016), with file papers/ReaxFF_others/Amiri_Ni_O_JCP_2016.pdf (distinct bytes from [[2016amiri-venue-oxidation-nickel]] / Amiri_NiO_impact_JCP_2016.pdf). The publication uses reactive molecular dynamics with ReaxFF to study hyperthermal oxidation of Ni(100) and Ni(111) by O₂ impacts at 5 eV translational energy with surface temperatures 300, 600, and 900 K. The work examines where oxide nuclei first appear, whether island-growth kinetics apply, oxygen uptake vs temperature, and the amorphous character of the growing NiO film via radial distribution functions, oxygen density profiles, and charge profiles across Ni | NiO. The introduction situates nickel alloys and NiO in corrosion-resistant and device contexts and contrasts hyperthermal exposure with conventional thermal oxidation—a framing that motivates the successive impact protocol used in the simulations.

Methods

This slug is a second ingested PDF for the same J. Chem. Phys. article as [[2016amiri-venue-oxidation-nickel]] (DOI 10.1063/1.4945421). The simulation protocol is identical in scientific content; only pdf_path / pdf_sha256 differ at the corpus layer.

MD application (atomistic dynamics)

The scientific protocol matches [[2016amiri-venue-oxidation-nickel]] (same DOI, different ingested PDF bytes). LAMMPS with variable-charge ReaxFF treats Ni(100) in a (9×9) surface cell (162 surface Ni atoms) and Ni(111) in (7×7) (196 surface Ni atoms), each with eight Ni layers. Surfaces are periodic in-plane; O₂ approaches along the non-periodic Z direction. After 20 ps Berendsen equilibration (0.1 ps damping) at 300, 600, or 900 K, trajectories use 10 ps NVE relaxation, then 200 successive 5 eV O₂ impacts (2.5 ps spacing, random in-plane placement) with Berendsen cooling between impacts to remove excess energy. Integration uses velocity Verlet with Δt = 0.25 fs. Barostat / controlled pressure: N/A — not used in the documented hyperthermal impact workflow.

Force-field training

N/A — application paper (same as sibling slug).

Static QM / DFT

N/A — same as sibling slug (QM appears as reference data for parameterization context, not AIMD production for the impacts).

Findings

The duplicate PDF does not change the abstract-level conclusions: oxide nuclei at arbitrary impact sites, Langmuir-like growth kinetics preferred over island-growth under these hyperthermal conditions, ~18.75% / ~23% increased oxygen consumption on Ni(100) / Ni(111) from 300 → 900 K, and an amorphous NiO film by RDF/density metrics after 200 O₂ impacts per supercell.

  • Comparisons: The introduction contrasts hyperthermal oxidation with prior thermal island-growth literature; quantitative agreement statements should be taken from pdf_path, not duplicated here.
  • Sensitivity: Trends are keyed to surface temperature (300–900 K) and impact energy (5 eV as modeled).
  • Limitations / outlook: Hyperthermal beams are a specific aerospace-motivated boundary condition; extrapolation to long-time corrosion requires bridging models beyond this paper’s scope.
  • Corpus honesty: This slug exists because two PDFs share one DOI; always cite pdf_path when quoting pagination, and prefer [[2016amiri-venue-oxidation-nickel]] for primary narrative unless you are auditing checksums.

Limitations

Two PDFs for one DOI require explicit checksum discipline. Hyperthermal conditions model energetic oxygen exposure rather than thermal Langmuir–Hinshelwood oxidation alone. Successive impacts build oxide films far from thermodynamic equilibrium thicknesses expected from slow thermal oxidation at the same T; extrapolate to long-time corrosion only with explicit kinetic bridging models.

Relevance to group

Reactive MD / ReaxFF line of work on metal oxidation under hyperthermal oxygen relevant to aerospace and surface science.

Citations and evidence anchors

Reader notes (navigation)