Skip to content

ReaxFF-based molecular dynamics study of bio-derived polycyclic alkanes as potential alternative jet fuels

Summary

ReaxFF MD is used to study early-stage pyrolysis of bio-derived head-to-head polycyclic alkanes HtH-1 (C₁₈H₃₂) and HtH-2 (C₁₈H₃₄) as high energy-density aviation fuel candidates. The motivation is to connect molecular architecture—two cyclohexyl units joined head-to-head—to decomposition kinetics and early gas-phase products relevant to combustor feed chemistry. The work extracts global Arrhenius parameters, maps temperature-dependent bond-scission mechanisms, compares product slates (including sooting propensity proxies), and examines binary mixtures where the two components react largely unimolecularly with weak cross-talk, supporting interpretation of how stereochemistry and hydrogen count steer branching versus concerted fragmentation.

Methods

1 — MD application (ReaxFF pyrolysis in LAMMPS). ReaxFF reactive molecular dynamics is run in the LAMMPS ecosystem for head-to-head polycyclic alkanes HtH-1 and HtH-2 (and binary mixtures) in periodic vapor-like cells that typically hold O(10¹–10²) fuel molecules per setup (e.g. ~40 molecules in the protocol described in the uncorrected-proof sibling and confirmed in the version-of-record tables); see Fuel 2020 for ρ, T, and composition (not re-tabulated here). The manuscript uses an in-house reaction-analysis pipeline on bond-order-updated connectivity to identify pathways and species yields vs T. Kinetics: global Arrhenius parameters are fit to summary reaction rates as defined in the article. N/A in this short note: full table of time step (fs), equilibration (ps), production (ns), thermostat (e.g. Berendsen), and barostat—use pdf_path for exact MD settings. Target temperature (K) for pyrolysis runs (e.g. 1500–3000 K window in the galley-level notes elsewhere in the corpus for this DOI): take from the Fuel article / SI (not re-typed here). Barostat (NPT) or fixed ρ (NVT at target ρ): per the published protocol (often NVT-style constant-volume heating in this corpus line). E-field / umbrella / replica sampling: N/A—not the focus here.

2 — Force-field training. N/A—applies an established ReaxFF for C/H hydrocarbon chemistry (as cited in the article), not a new fit in this publication.

3 — Static QM / DFT-only. N/A—result trajectories are ReaxFF MD; any QM in the paper is for reference or validation, not the headline sampling method.

Findings

  • HtH-1 pyrolyzes faster than HtH-2 under matched T, ρ conditions, and both can exceed some conventional benchmarks such as JP-10 in the compared decomposition metrics (per abstract).
  • Low T: Central C–C bond between cyclohexyl units dominates initial scission for both fuels.
  • High T: C–CH₃ bond breaking becomes dominant due to entropy-favored fragmentation channels.
  • Major products: HtH-1 favors C₅H₈ and C₄H₈; HtH-2 favors C₄H₈ and C₂H₄; product slates imply higher sooting tendency for HtH-1, consistent with experiments quoted by the authors.
  • Mixtures: Unimolecular decomposition with little intermolecular coupling between HtH-1 and HtH-2 under their pyrolysis conditions, which the authors interpret as weak binary reactivity under the simulated heating protocols.

Limitations

ReaxFF kinetics are empirical; extrapolation to flame conditions and soot chemistry requires separate validation against experiment and higher-level theory. Operator note: when citing Arrhenius parameters or product yields, align numbers with the Fuel version-of-record PDF and SI tables rather than secondary summaries; mixture simulations here probe weak coupling between HtH isomers but do not replace engine spray or oxidizer coupled kinetics.

Relevance to group

Direct PSU van Duin-group contribution to sustainable aviation fuel chemistry using ReaxFF pyrolysis workflows.

Citations and evidence anchors

Reader notes (navigation)