High temperature oxidation of monolayer MoS2 and its effect on mechanical properties: A ReaxFF molecular dynamics study
Scope
ReaxFF reactive MD of basal-plane oxidation of monolayer MoS\(_2\) at 1400–1800 K, followed by tensile tests comparing pristine versus oxidized structures; reports 2H→1T transitions under load.
Summary¶
Reactive molecular dynamics with ReaxFF is used to follow high-temperature oxidation of monolayer MoS\(_2\) on the basal plane and to quantify consequences for mechanical response. Simulations explore oxidation kinetics at 1400 K, 1500 K, and 1800 K with O\(_2\) present, finding facile reaction above about 1500 K beginning with O\(_2\) adsorption atop sulfur and progressing toward an oxy-sulfide MoS\(_{2-x}\)O\(_x\) solid solution. Uniaxial tensile simulations show degradation of fracture strength, fracture strain, Young’s modulus, and fracture toughness upon oxidation relative to pristine sheets. Both pristine and oxidized systems exhibit a transition from trigonal prismatic 2H-MoS\(_2\) to a distorted octahedral 1T-like metallic phase during the mechanical tests reported. Fracture pathways are analyzed from atomic trajectories. Oxidation converts sulfide to oxy-sulfide phases that weaken the basal plane—relevant to flexible electronics and tribological coatings exposed to air; stress-induced 2H→1T-like transitions couple chemistry to mechanical phase behavior in the simulated monolayers. For authoritative numbers, use the version-of-record PDF and Supporting Information.
Methods¶
1 — MD application (ReaxFF RMD). Reactive molecular dynamics is performed in LAMMPS with the Mo–S–O ReaxFF parameter set referenced in Surfaces and Interfaces for monolayer MoS\(_2\) oxidation and follow-on mechanics. The in-plane supercell contains O\(_2\) above the basal surface; PBC apply in the periodic cell. NVT trajectories with a thermostat (details and timestep in fs in the article) run equilibration and production stages whose lengths are given in ps/ns; temperature is held at 1400 K, 1500 K, and 1800 K to study oxidation kinetics. Barostat / pressure control: N/A — not the focus of the excerpted NVT oxidation protocol; N/A — external electric field; N/A — umbrella / metadynamics / replica enhanced sampling in the reported work. Uniaxial tensile tests on pristine versus oxidized structures use the same code base; authors report fracture strength, strain at failure, Young’s modulus, and fracture toughness, and track 2H vs 1T-like distortions along atomic trajectories.
2 — Force-field training. N/A — the study applies a published ReaxFF description to MoS\(_2\) + O\(_2\); it is not a new ReaxFF parameterization paper.
3 — Static QM. N/A — not used as the main engine; oxidation and mechanics are ReaxFF-based.
4 — Experiments. N/A — computation-only in the work summarized here.
Findings¶
- Oxidation initiates via O\(_2\) adsorption on sulfur and advances to oxy-sulfide formation; reactivity increases strongly above ~1500 K in the simulations described.
- Oxidation reduces multiple tensile and fracture metrics relative to pristine monolayer MoS\(_2\).
- Stress-driven 2H→1T transitions appear for both pristine and oxidized samples in the reported tests.
- Atomic-scale fracture sequences are documented for comparison between oxidized and unoxidized cases.
Comparisons & sensitivity. Oxidized films are compared to pristine monolayers on multiple mechanical metrics. Oxidation reactivity and mechanical degradation depend strongly on temperature in the 1400–1800 K window studied.
Limitations (corpus). The abstract-level summary here does not restate every numerical control; confirm timestep, O\(_2\) coverage, and run lengths in the PDF/SI when citing protocols.
Limitations¶
High-temperature, idealized monolayer setups omit full environmental complexity (e.g., humidity, defects other than those formed during oxidation in the model).
Relevance to group¶
Application-focused ReaxFF study for TMD oxidation and mechanics under extreme thermal conditions.