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ReaxFF Simulation of Pyrolysis Behaviors of Polysiloxane Precursors with Different Carbon Content

Evidence and attribution

Authority of statements

Prose sections below (Summary, Methods, Findings, etc.) are curated summaries of the publication identified by doi, title, and pdf_path in the front matter above. They are not new primary claims by this wiki.

Summary

This Chemistry of Materials article uses LAMMPS molecular dynamics with a ReaxFF reactive potential to simulate pyrolysis of polysiloxane precursors with different carbon content, aiming to quantify atomistic routes from polymer to silicon oxycarbide ceramic products. The authors motivate the study by noting that polymer-derived ceramics are technologically attractive but that experiments often cannot fully resolve atomic-scale bond rearrangements, cluster formation, and domain sizes during conversion. The manuscript states that it is among the first efforts to quantify the atomic evolution of polymer-to-ceramic conversion for the chosen precursors, with emphasis on ceramic composition, yield, bond populations, radial distribution functions, and the sizes of silicon–oxygen-rich versus carbon-rich regions in the final models.

Methods

Reactive force field and software (A/B)

  • Potential: ReaxFF for Si–O–C–H chemistry in LAMMPS.
  • Precursors: PDMS, PDES, and SPR-684 PSO—spanning different carbon content and side-group architecture on a siloxane backbone.

Pyrolysis MD protocol (B)

  • System size: ~10⁵ atoms (order-of-magnitude statement in the article), larger than many prior ReaxFF pyrolysis benchmarks cited by the authors.
  • Temperature window: 1500–2100 K (intended as more realistic than some ultra-high-T prior studies).
  • Gas handling: Periodic removal of small volatile molecules using molecular-weight / deletion rules described in Methods (affects final stoichiometry if mishandled).

Analysis

Ceramic yield, elemental composition, bond-type populations, RDFs, cluster sizes for Si–O-rich vs C-rich domains, and residual H content.

MD application (integrated)

Engine / code: LAMMPS with ReaxFF for Si–O–C–H pyrolysis. System & composition: order ~10⁵ atoms and PDMS / PDES / SPR-684 PSO precursor stoichiometry in Chemistry of Materials Methods. PBC for 3D bulk pyrolysis cells. Temperature program: 1500–2100 K heating window (as reported). Ensemble, timestep, thermostating, total burn-off duration, volatile deletion cadence, barostat, pressure, field, enhanced sampling (metadynamics/REX/umbrella): N/A in this short summary—read the peer-reviewed article for the NVT/NVE-style stages and timestep/duration in ps/ns; N/A — static electric field; N/A — enhanced sampling in the main protocol.

Findings

Composition–structure mapping

Final ceramic composition tracks initial polymer composition, linking side-group chemistry to carbon retention and networking.

Carbon networking vs scission

Carbon-rich precursors build C–C connectivity via loss of Si–O, Si–C, and C–H; less carbon-rich precursors may lose C–H with limited C–C formation in the highlighted stages.

Domains and RDFs

Si–O-rich vs C-rich domains differ in size and connectivity at the atomic scale; RDFs show more C–C bonding at higher T, while C–H can persist even at 2100 K and long-range crystallinity does not emerge in their models.

Experimental context (intro)

The article cites experimental silicon oxycarbide literature on Si–C scission thresholds and phase separation at high temperature to motivate temperature choices and RDF interpretation.

Limitations

ReaxFF accuracy for siloxane→ceramic chemistry should be checked against QM/experiment where available.

Relevance to group

Polymer-derived ceramic pyrolysis mapped with ReaxFF in the organosilicon lineage.

Citations and evidence anchors

Reader notes (navigation)