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Improved ReaxFF force field parameters for Au–S–C–H systems

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Prose below summarizes the publication identified by doi, title, and pdf_path.

Summary

ReaxFF Au–S–C–H parameters are reoptimized from an earlier Järvi et al. set (2011). Au–S, Au–Au, and S–Au–S bending terms are adjusted to improve bond-bending PES behavior. The updated field reproduces PBE geometries for small clusters and gold–thiolate nanoparticles; Au₃₈(SCH₃)₂₄ isomer energetics align with PBE ordering; Au₄₀(SCH₃)₂₄ and SAM-like models are sampled with the new parameters (abstract claims). Thiolated Au nanoparticles are ubiquitous in sensing and drug-delivery models; improving staple motif bending surfaces matters because Au–S coordination changes feed into facet stability and ligand exchange pathways.

Methods

DFT reference: Amsterdam Density Functional (ADF) with PBE, triple-ζ polarized (TZP) basis, scalar relativistic ZORA, frozen cores as stated (Au core through 4f, S through 2p, C through 1s). Cluster geometries and single-point energies feed the ReaxFF reoptimization starting from Järvi et al. 2011 Au–S–C–H parameters.

ReaxFF / MD: All ReaxFF runs use LAMMPS; NVE relaxation to 0 K is mentioned with 100 Å cubic periodic cells for Au/S/C/H tests in the Computational section excerpt.

Fitting focus: Adjust Au-S, Au-Au, and S-Au-S bending terms so staple -S-Au-S- motifs can approach the near-linear PBE minimum (Figure 1 PES). Parameter tables: [[2013aikens-venue-si8]] / [[2013aikens-venue-si8-2]].

MD application

Engine / code: LAMMPS molecular dynamics for ReaxFF validation (Computational Details; extract).

System & composition: 100 Å × 100 Å × 100 Å periodic cells for selected Au/S/C/H tests; nanoparticle and SAM examples in the article body (abstract/Results).

Boundaries / periodicity: 3D periodic cubic cells for the cited MD relaxation tests.

Ensemble: NVE relaxation toward 0 K as stated in the Computational section excerpt.

Timestep: N/A — numerical Δt (fs) not recovered from 2013bae-j-phys-chem-jp405992m_p1-2.txt—see pdf_path.

Duration / stages: N/A — total ps/ns schedule not in the short extract.

Thermostat / barostat: N/A — not stated for the NVE relaxation description on indexed pages.

Temperature: N/A — explicit thermostat targets for all MD snippets not in the excerpt.

Pressure: N/A — not stated for these NVE cells in the excerpt.

Electric field: N/A — not used.

Replica / enhanced sampling: N/A — not used.

Findings

Outcomes: NP-specific ReaxFF reproduces PBE geometries for small Au–thiolate clusters and improves S–Au–S bending PES relative to Järvi et al. 2011 (abstract). Au\(_{38}\)(SCH\(_3\))\(_{24}\) isomer orderings match PBE, and larger Au\(_{40}\)(SCH\(_3\))\(_{24}\) plus SAM-like models are sampled with the updated field (abstract).

Comparisons: Benchmarks are primarily versus PBE training data; introduction cites experimental cluster literature for motivation.

Sensitivity / levers: Accuracy hinges on staple vs bridge motifs and bending angles along the CH\(_3\)–S–Au–S–CH\(_3\) scan highlighted in Figure 1.

Limitations: PBE-centric training; explicit solvent, electrode potentials, and electrochemical environments are outside the gas-phase/cluster emphasis (see Limitations on this page).

Corpus honesty: Duplicate wiki slug [[2013bae-venue-jp405992m]] shares the DOI; confirm pdf_sha256 before merging manifests.

Limitations

PBE training scope; nanoparticle isomer space incomplete in any finite study. Explicit solvent, electrode potentials, and image charge effects in electrochemical environments are not treated in the gas-phase/periodic cluster setups emphasized in the parameterization paper. Relativistic corrections beyond the ZORA scheme employed may matter for quantitative binding on very small Au clusters.

Relevance to group

Gold–thiolate ReaxFF line used broadly in nanoparticle and SAM simulations adjacent to group metal/organic interfaces.

Citations and evidence anchors

  • DOI 10.1021/jp405992m — J. Phys. Chem. A 117, 10438–10446 (2013).
  • Extract: normalized/extracts/2013bae-j-phys-chem-jp405992m_p1-2.txt.

Reader notes (navigation)

Duplicate corpus paths sometimes exist for the same DOI; prefer the pdf_path on this page when resolving hashes and chunks.