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Growth kinetics and atomistic mechanisms of native oxidation of ZrSₓSe₂₋ₓ and MoS₂ crystals

Summary

Spectroscopic ellipsometry on cleaved bulk ZrSₓSe₂₋ₓ alloys vs MoS₂ tracks native oxide growth; ReaxFF reactive MD (with first-principles checks in the Supporting Information) interprets O₂ chemisorption, Zr–O network formation, chalcogen redox, and SO₂ formation. Zr-based alloys oxidize rapidly in air with rate increasing in Se content; MoS₂ basal surfaces remain essentially non-reactive on laboratory timescales under the reported conditions. The paper couples ellipsometry kinetics with atomistic Zr vs Mo contrasts in the MD narrative.

Methods

  • Experiments: Ambient oxidation of cleaved bulk crystals; spectroscopic ellipsometry for sub-nm oxide thickness evolution (see article).
  • Atomistics: ReaxFF parameterization for Mo/Zr/S/O (development and benchmarks summarized in SI); reactive MD trajectories at representative temperatures (including 800 K short runs and 1500 K longer runs discussed for SO₂ evolution in the main text).
  • Validation: Authors reference first-principles quantum molecular dynamics comparisons for key ZrS₂ oxidation steps (figures cited in SI).

Cell sizes, ReaxFF parameter tables, thermostat/barostat choices, and analysis scripts for oxide thickness trends are detailed in papers/ReaxFF_others/Jo_Sungwook_acs.nanolett_2020_ZrSSe_MoS2.pdf and the article Supporting Information.

MD application (ReaxFF). ReaxFF reactive molecular dynamics of O₂ with ZrSₓSe₂₋ₓ and MoS₂ basal slabs in 3D PBC (atom counts in pdf_path and SI). The main text contrasts ~800 K short trajectories (order ~tens of ps in the article) and ~1500 K longer runs (order ~hundreds of ps to ns—confirm in pdf_path) for SO₂ formation and egress. N/A — exact fs timestep in this wiki; see SI. Ensemble: NVT-like thermostated ramped-T oxidation (see article). Barostat: N/A — not a high-pressure shock cell in the quoted protocol summary. Pressure (MD): 1 bar-scale laboratory ambient (ellipsometry) is separate from the O₂ / thermostats in ramped ReaxFF; N/A — see pdf_path for O₂ chemical environment details. Electric field: N/A — not used. Umbrella / metadynamics / replica exchange: N/A — not in the summarized ramped-T protocols here.

Findings

  • ZrSₓSe₂₋ₓ basal oxidation initiates with favorable O₂ adsorption followed by Zr–O bond switching and gap collapse; chalcogen sites undergo successive redox transitions during oxygen ingress.
  • SO₂ formation and egress appear as the slow step in the mechanism narrative; 1500 K simulations observe SO₂ escape whereas 800 K runs are too short to capture full egress in the showcased trajectory.
  • MoS₂ shows unfavorable oxygen chemisorption on basal planes under the model, consistent with slow oxidation in experiment.

The authors emphasize interpreting accelerated MD temperatures as qualitative mechanistic guides paired with room-temperature experimental oxidation rates. Corpus honesty: pull reproducible MD settings from pdf_path and SI; an alternate PDF path is [[2020seong-soon-jo-nano-lett-20-growth-kinetics]].

Limitations

High-temperature MD used to accelerate chemistry; direct mapping to room-temperature kinetics requires care. Force-field accuracy for Zr–S–Se–O chemistry is benchmarked but remains empirical.

Wiki prose here is a navigation aid. Definitive numbers, protocol details, and figure-level claims should be taken from the peer-reviewed article at pdf_path (and any Supporting Information cited there), not from this page alone.

Relevance to group

Included as ReaxFF_others corpus reference; no van Duin authorship—useful comparative context for TMD oxidation and ReaxFF validation practices.

Reader notes (navigation)