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A reactive molecular dynamics study of n-heptane pyrolysis at high temperature

Evidence and attribution

Authority of statements

Sections below summarize the publication identified by doi, title, and pdf_path in the front matter.

Summary

ReaxFF-based reactive MD is used to study gas-phase pyrolysis of n-heptane at very high temperatures (multi-thousand Kelvin regime in the reported simulations). The work emphasizes a radical-dominated mechanism with unimolecular C–C fission as the principal initiation channel, nonuniform scission propensity along the carbon chain (central C–C bonds preferentially), and qualitative support for Rice–Kossiakoff-type decomposition organization at the atomistic level. Apparent activation energies extracted from simulation kinetics fall in the ~43–54 kcal/mol range for the sampled temperature window, described as broadly consistent with experimental high-temperature pyrolysis literature.

Methods

1 — MD application (atomistic dynamics). Engine / code: Reactive molecular dynamics (RMD) with ReaxFF as described in Computational Details (explicit package name—e.g., LAMMPS—should be confirmed in pdf_path; the indexed excerpt emphasizes ReaxFF RMD). System size & composition: unimolecular cells contain one n-heptane molecule in a 20 Å × 20 Å × 20 Å periodic cube (~10¹–10² atoms class); multimolecular cells contain 16 n-heptane molecules per periodic box (~10³ atoms class), with trajectory-count convergence tests reported in the article (>~140 trajectories for unimolecular statistics; ≥9–12 trajectories for multimolecular observables depending on the quantity). Boundaries / periodicity: three-dimensional periodic cubic cells (PBC). Ensemble: NVT MD. Timestep: 0.1 fs. Duration / stages: multiple independent trajectories and staged annealing/heating workflows are described in pdf_path (full schedule not reproduced in normalized/extracts/2013ding-venue-jp311498u_p1-2.txt). Thermostat: Berendsen-style coupling with 0.05 ps temperature damping constant as stated in Computational Details. Barostat: N/A — gas-phase NVT protocol without Parrinello–Rahman pressure control. Temperature: 2400–3000 K window emphasized for multimolecular kinetics analysis in the wiki summary; additional temperatures may appear in the full Methods. Pressure: N/A — not used as an explicit MD control variable in the summarized NVT gas-phase setup. Electric field: N/A — not reported. Replica / enhanced sampling: N/A — not reported. Electrostatics / cutoffs: N/A — not recovered from the indexed excerpt (confirm in pdf_path if relevant). Species detection: bond-order cutoff 0.3.

2 — Force-field training. N/A — uses published C/H/O ReaxFF parameters from van Duin / Chenoweth “without modification” (article wording in the extract).

3 — Static QM / DFT. N/A — QM is referenced only as historical context for ReaxFF parameter origins in the extract; this is not a DFT-application study.

Findings

1 — Outcomes & mechanisms. Pyrolysis is radical-dominated; unimolecular decomposition proceeds primarily via C–C bond fission, with central C–C bonds breaking preferentially over terminal bonds in the sampled statistics (abstract/extract).

2 — Comparisons. Multimolecular product and intermediate distributions are compared qualitatively to several experimental n-heptane pyrolysis studies cited in the article (see pdf_path for species lists).

3 — Sensitivity & design levers. Temperature (2400–3000 K for the quoted Ea window), unimolecular vs multimolecular setup, and trajectory ensemble sizes are the main levers discussed for converged statistics.

4 — Limitations & outlook. The Discussion notes that additional intermolecular channels would be needed for richer dense-phase modeling beyond the gas-phase supercells emphasized here (article framing).

5 — Corpus honesty. Parallel corpus registration may exist as [[2013heptane-venue-jp311498u]]; numerical values should be verified against pdf_path for the paginated J. Phys. Chem. A article (DOI in front matter).

Limitations

  • Extremely high simulated temperatures and short timescales constrain direct comparison to engine-relevant lower-temperature chemistry; force-field fidelity for radical-rich networks is scenario-dependent.

Relevance to group

Corpus fuel pyrolysis reference using the widely circulated hydrocarbon ReaxFF parameter lineage associated with the group’s foundational papers.

Citations and evidence anchors

  • Abstract and methods: force-field citation, temperature ranges, Ea extraction (J. Phys. Chem. A; DOI above).

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