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Accelerated ReaxFF simulations for describing the reactive cross-linking of polymers

Summary

Thermoset epoxy–amine curing is a workhorse materials workflow, but atomistic modeling stalls when reaction barriers make spontaneous cross-linking rare at practical temperatures within accessible MD times. This registry corresponds to a second proof PDF variant in the corpus for the J. Phys. Chem. A article on accelerated ReaxFF cross-linking of a bis-F / DETDA-type network, where restraint/bond-boost–style energy injection helps traverse bottlenecks while parameters are refined starting from CHNO-2017_weak and QM benchmarks the epoxide–amine pathways. The scientific content matches the curated version-of-record page [[2018vashisth-j-phys-chem-accelerated-reaxff]], which should be cited for publisher pagination, SI references, and experimental comparisons (density, \(T_g\), modulus). This path exists for byte-level provenance when multiple proof PDFs share a DOI. For readers, the substantive scientific story is unchanged: accelerated reactive sampling is used to build epoxy–amine networks, then thermomechanical properties are compared to dogbone experiments on the same chemistry, demonstrating that ReaxFF can span cure chemistry and engineering moduli in one model family when parametrized carefully. Maintainers keep this duplicate slug because large corpora often ingest multiple proof uploads with identical DOI but different byte histories; the wiki still needs a faithful, reader-safe summary even when the primary curation lives on the VOR page. When in doubt, prefer [[2018vashisth-j-phys-chem-accelerated-reaxff]] for any quantitative comparison to experiments, and use this note primarily for provenance, navigation, and duplicate-PDF bookkeeping. See the VOR page for modulus and \(T_g\) numbers.

Methods

Duplicate proof ingest for DOI 10.1021/acs.jpca.8b03826; scientific protocol matches [[20180000-0002-4740-1296-x-accelerated-reaxff]] and the version-of-record page [[2018vashisth-j-phys-chem-accelerated-reaxff]].

A — Force-field training / QM benchmarks

  • ReaxFF parametrization for epoxide–amine cure chemistry with QM checks on three transition-state families (abstract); parameter tables may appear in [[2018vashisth-venue-microsoft-word]] / SI depending on publisher packaging.

B — Accelerated reactive MD + property evaluation

  • LAMMPS workflows: accelerated cross-linking at low temperature; network annealing; NPT runs for density and \(T_g\); mechanical tests for modulus—full integration settings on the VOR/SI because proof PDFs can differ in pagination and figure quality.

C — Experiments

  • Experimental cure/dogbone characterization cross-referenced in the J. Phys. Chem. A article for density, \(T_g\), and modulus comparisons.

MD protocol (aligned with VOR article)

  • Engine / code: LAMMPS molecular dynamics with ReaxFF as on 2018vashisth-j-phys-chem-accelerated-reaxff / 20180000-0002-4740-1296-x-accelerated-reaxff.
  • System size & composition: Periodic cells with thousands of atoms for bis-F/DETDA curing (Methods/SI on the VOR).
  • Boundaries / periodicity: 3D PBC bulk setups.
  • Ensemble: NVT and NPT stages for cross-linking, annealing, and property runs per JPCA Methods.
  • Timestep: Sub-picosecond timestep in fs as tabulated on the VOR (not re-derived from this proof bytes).
  • Duration: Equilibration and production segments totaling nanoseconds of sampling where reported.
  • Thermostat: Nose–Hoover or Berendsen as stated in the article.
  • Barostat: NPT barostat when pressure in bar is controlled for density/T_g windows; otherwise NVT at constant volume.
  • Temperature: K setpoints for cure-relevant stages on the VOR.
  • Pressure: NPT targets in bar when used; N/A for strict NVT segments without barostat coupling.

Findings

Outcomes match the version-of-record page: QM-consistent reaction barriers, ~82% cross-linking, and density/T_g/Young’s modulus in line with dogbone experiments within uncertainties quoted there. Temperature- and strain-dependent rejection of accelerated moves is noted in the abstract. Limitations: cite 2018vashisth-j-phys-chem-accelerated-reaxff for pagination; this proof PDF is duplicate corpus provenance only (corpus honesty).

Limitations

Retain this slug for provenance; cite [[2018vashisth-j-phys-chem-accelerated-reaxff]] for canonical pagination and bibliographic details.

Relevance to group

Duplicate corpus path for the same PSU ReaxFF polymer methodology paper.

Citations and evidence anchors

Reader notes (navigation)