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A reactive molecular dynamics study of n-heptane pyrolysis at high temperature (alternate corpus PDF)

Alternate corpus PDF bytes for Ding et al., J. Phys. Chem. A on ReaxFF pyrolysis of n-heptane (DOI 10.1021/jp311498u); one curated science narrative lives on 2013ding-venue-jp311498u.

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Prose summarizes the publication identified by doi. Full section-level detail aligns with 2013ding-venue-jp311498u.

Summary

ReaxFF-based reactive molecular dynamics studies gas-phase pyrolysis of n-heptane at very high simulated temperatures (multi-thousand Kelvin). The work emphasizes a radical-dominated mechanism with unimolecular C–C fission as the principal initiation channel, nonuniform scission along the chain (central C–C bonds preferentially), and qualitative consistency with Rice–Kossiakoff-style organization. Apparent activation energies from simulation kinetics fall near 43–54 kcal mol⁻¹ over the sampled temperature window, described as broadly consistent with experimental high-temperature pyrolysis literature.

The article contrasts single-molecule unimolecular cells with multimolecular periodic boxes to probe bimolecular channels and product distributions, acknowledging that the very high simulated temperatures accelerate chemistry relative to engine-relevant conditions while still allowing comparison to literature pyrolysis product trends.

Methods

1 — MD application. Reactive molecular dynamics uses the ReaxFF implementation with C/H/O parameters from van Duin and Chenoweth without modification (papers/ReaxFF_others/Heptane_pyrolysis_JPCA_2013.pdf; same science as 2013ding-venue-jp311498u). Engine: LAMMPS-class RMD workflow as in the article. System: one n-heptane molecule (C₇H₁₆, 23 atoms) in a 20 Å cubic cell for unimolecular pyrolysis; multimolecular boxes pack 16 molecules (total atom count scales accordingly) with PBC. Ensemble: NVT. Timestep: 0.1 fs. Thermostat: Berendsen-style coupling with 0.05 ps damping as reported. Temperature: multi-thousand-K pyrolysis window with rate analysis at 2400–3000 K in the multimolecular workflow. Species detection: bond-order cutoff 0.3. Barostat / hydrostatic pressure: N/A — constant-volume NVT legs described above. Electric field: N/A. Replica / enhanced sampling: N/A — brute-force MD trajectories (no umbrella/metadynamics/replica exchange summarized here). Duration: ps/ns segment lengths for equilibration vs production as tabulated in the PDF (not retyped here).

2 — Force-field training. N/A — this entry applies the published C/H/O ReaxFF library; parameter fitting is not the focus of this pyrolysis application paper.

3 — Static QM. N/A — not the primary methodology for the pyrolysis study summarized here.

Findings

Outcomes & mechanisms: Pyrolysis is radical-dominated with unimolecular C–C fission as the main initiation channel; central C–C bonds cleave preferentially over terminal bonds in the sampled statistics. Multimolecular product distributions overlap key species from experimental pyrolysis literature despite higher simulated temperature.

Comparisons: Apparent activation energies 43.02–54.49 kcal mol⁻¹ over 2400–3000 K are discussed against experimental high-temperature cracking references in the article.

Sensitivity / design levers: Temperature window and uni- vs multimolecular cell choice change product channels and inferred kinetics; dense-phase chemistry would require additional intermolecular pathways beyond the gas-phase cells summarized.

Limitations & outlook: Very high simulated temperature accelerates chemistry relative to engine-relevant conditions; short trajectories may miss slow channels—see authored discussion in the PDF.

Corpus honesty: This slug is an alternate corpus PDF for DOI 10.1021/jp311498u; confirm numbers against the version-of-record narrative on 2013ding-venue-jp311498u if pagination differs.

Limitations

Two PDFs with different SHA-256 values may reflect publisher layout differences; cite the DOI, not a specific file hash, for external scholarship. High temperatures and short timescales limit direct comparison to lower-temperature engine chemistry.

Relevance to group

Manifest bookkeeping for an alternate acquisition path for the same hydrocarbon ReaxFF pyrolysis reference.

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