Supplementary information: Nanoparticle activated and directed assembly of graphene into a nanoscroll
Summary¶
This Supporting Information PDF papers/ReaxFF_others/Bejagam_Carbon_nanoscroll_2018_SI.pdf accompanies the Carbon article DOI 10.1016/j.carbon.2018.03.077 on nanoparticle-directed rolling of graphene into nanoscrolls (Bejagam, Singh, Deshmukh). Section S1 in the extract explains why ReaxFF is used: it captures association and dissociation, charge transfer between cations and anions, and nonbonded interactions, with parameters typically fit to large QM databases for ground and reactive pathways. Equation S1 lists \(E_{\text{total}} = E_{\text{bond}} + E_{\text{over}} + E_{\text{under}} + E_{\text{val}} + E_{\text{pen}} + E_{\text{tors}} + E_{\text{conj}} + E_{\text{vdWaals}} + E_{\text{Coul}}\), and notes that nonbonded interactions are computed for all atom pairs with shielding to avoid excessive short-range repulsion. The SI traces provenance for graphene–diamond (hydrocarbon/nitramine-extended training cited), graphene–nickel (Muller et al. following Nielson et al. CNT-on-Ni development), graphene–platinum (Sanz-Navarro et al.), and graphene–gold (Jarvi et al.), stating each block was trained against QM interaction energies for sp² carbon on the respective metals.
Methods¶
The SI is methodological documentation: it does not replace the main article’s simulation protocol. The extract elaborates nickel–carbide training cases (Ni₃C, Ni₂C, NiC phases) used in Muller et al.’s improvement to Ni-catalyzed hydrocarbon chemistry and notes validation of a graphene sheet on Ni against QM. Production reactive NVT LAMMPS runs—300 K, 0.5 fs timestep, ~5 ns duration, 300 Å cubic cell with a fixed graphene strip edge—are summarized on 2018bejagam-carbon-134-2-nanoparticle-activated together with nanoparticle compositions (diamond, nickel, platinum, gold) that nucleate scrolling.
- Boundaries / periodicity: Three-dimensional periodic boundary conditions on the 300 Å cubic cell; frozen graphene edge atoms as in the main article figures.
- Thermostat: NVT thermal control at 300 K (implementation per Carbon Methods / SI inputs).
- Barostat / pressure: N/A — constant-volume NVT RMD; N/A — no target hydrostatic pressure in the summarized scroll protocol.
ReaxFF training documentation (SI, not a standalone refit in this work): Parent parameter sets combine literature ReaxFF blocks for hydrocarbon / nitramine (graphene–diamond), Muller et al. Ni chemistry (graphene–Ni), Sanz-Navarro et al. Pt clusters (graphene–Pt), and Jarvi et al. Au–organics (graphene–Au), each trained against DFT/QM interaction energies for sp² carbon on the corresponding metal (Section S1). Training sets emphasize QM databases of bond dissociation, equation of state data, and surface-cluster energies as cited per block. Optimization: N/A — this SI documents merged literature parameters rather than a new global parameter optimization run for the nanoscroll study. Validation: authors point to QM benchmarks (e.g., graphene on Ni) used when those blocks were originally published.
Findings¶
Scroll formation timelines, radii, and comparative nanoparticle efficiencies appear in the primary article; this SI substantiates ReaxFF force-field choices and energy decomposition underpinning those simulations. The narrative emphasizes that Ni parameters encode surface/subsurface/bulk hydrocarbon binding and carbide formation energies, Pt parameters target cluster energies, and Au blocks stem from thiolate-focused QM training—each motivating why merged sets should describe sp² carbon on metals in the nanoscroll geometry. Compared to using a single metal–carbon table blindly, the SI stresses compatibility checks when mixing blocks. Sensitivity to NP composition and graphene edge constraints is implicit: users must import exact parameter tables from this PDF rather than secondary summaries. Limitations: merged subsets were not simultaneously reoptimized in one global fit for this specific geometry—an authored caveat relevant when porting parameters. Corpus honesty: this slug is SI-only; quantitative kinetics claims belong with the version-of-record article linked by DOI and 2018bejagam-carbon-134-2-nanoparticle-activated.
Limitations¶
Parameter provenance text references external studies; users must verify compatibility when mixing parameter blocks across publications.
Relevance to group¶
ReaxFF documentation for graphene–nanoparticle self-assembly relevant to nanocarbon mechanics and tribology themes.
Users combining multiple metal–carbon parameter sources should verify compatibility of charge equilibration settings across blocks, because the SI itself warns that ReaxFF merges QM-trained subsets that were not simultaneously reoptimized in a single global fit for this specific nanoscroll study.
Scroll initiation and barrier estimates in the main article should be reproduced with identical nanoparticle compositions and edge constraints, because the SI documents parameters but not every geometric variant tested during exploration.