Second-generation ReaxFF water force field: improvements in the description of water density and OH-anion diffusion

Corpus note

Maintainer catalog (SI/galley/proof PDF roles): https://github.com/asepehri93/vanDuinWiki/blob/main/docs/corpus/NON_PRIMARY_ARTICLE_PAPER_SLUGS.md The repository PDF filename references JPCC, while the extract footer lists J. Phys. Chem. B and DOI 10.1021/acs.jpcb.7b02548. Resolve any path/name mismatch against the publisher record you trust.

Summary¶

The authors present an improved second-generation ReaxFF water model (water-2017) built from the earlier water-2010 parametrization, targeting bulk water density, hydroxide transport, and acid/base proton-transfer chemistry in large-scale classical reactive MD. Molecular dynamics with water-2017 is used to probe Eigen–Zundel–Eigen style mechanisms for hydronium transport and the hypercoordinated solvation of OH\(^-\) in basic solution, and to reproduce relative diffusion constants for H\(_2\)O, H\(_3\)O\(^+\), and OH\(^-\).

Proton and hydroxide transport in water underpins electrochemistry from batteries to biophysics; ReaxFF water models must balance density, diffusion ordering, and acid/base reactivity in large cells. The water-2017 refinement targets hydroxide hypercoordination in base and Eigen–Zundel transport in acid, with explicit comparison to experimental diffusion constants for the three principal aqueous species. Consult the peer-reviewed PDF and any Supporting Information for authoritative tables, figures, and numerical diagnostics behind the summaries above.

Methods¶

Force-field training (ReaxFF). Water-2017 refits the earlier water-2010 ReaxFF description using quantum mechanical (QM) training data and parameter optimization workflows summarized in the JPCB article, targeting improved bulk density, OH⁻ diffusion, and acid/base proton transfer while retaining reactive MD stability.

Molecular dynamics (reactive). Molecular dynamics with water-2017 samples acidic and basic bulk electrolytes in periodic cells containing thousands of atoms, using NVT-class thermostat control near ambient pressure (≈1 bar), femtosecond timesteps, and extended production runs after equilibration to extract diffusion constants and Grotthuss/Eigen–Zundel motifs. Exact barostat usage, temperature (K) grids, and run duration (ps/ns) appear in papers/Zhang_ReaxFF_water_JPCC_2017_proof.pdf (note proof status) and its SI companion [[2017zhang-venue-microsoft-word]]. Electric fields and metadynamics/umbrella enhanced sampling are not highlighted in the abstract-level summary used here.

Static QM / DFT. DFT/QM targets underpin the training set; they are not used as production AIMD for the large-cell diffusion benchmarks.

Review scope. N/A — primary parameterization + validation paper; SI holds tabulated coefficients.

Findings¶

Outcomes and mechanisms. Water-2017 supports an Eigen–Zundel–Eigen picture for acidic proton transport and reproduces hypercoordinated OH⁻ solvation motifs in base, including the diffusion mechanisms emphasized in the abstract.

Comparisons. Simulated diffusion constants follow the experimental ordering H₂O < H₃O⁺ ≈ OH⁻ (context-dependent) and are reported to match experiment within the uncertainties quoted in the paper.

Sensitivity / design levers. At high OH⁻ concentration, H₃O⁺ and OH⁻ diffusivities converge because strong correlations among hydroxide ions alter the hydrogen-bond network, as noted in the abstract.

Limitations / outlook. Proof PDF filenames in this corpus may still read “JPCC” even though the footer lists JPCB—resolve against the publisher record you trust before citing venue strings.

Corpus honesty. Detailed MD diagnostics and tables live in the PDF/SI pair; this page summarizes abstract-level claims only.

Limitations¶

Proof PDF; detailed timestep, thermostat, and system sizes should be taken from the full article/SI.

Relevance to group¶

Core van Duin-group water ReaxFF line; underpins many subsequent electrolyte, mineral, and interface studies.

Parameter tables: 2017zhang-venue-microsoft-word.

Citations and evidence anchors¶

DOI from extract footer: 10.1021/acs.jpcb.7b02548.