Skip to content

Supporting Information: Development of the ReaxFF Methodology for Electrolyte–Water Systems

Summary

This PDF (papers/Fedkin_JPCA_Electrolyte_2019_SI.pdf) is the Supporting Information for Fedkin et al., J. Phys. Chem. A, on extending ReaxFF to alkali-hydroxide / oxide chemistry in electrolyte–water environments relevant to energy storage and aqueous electrochemistry. The extract begins with Section S1 heading “ReaxFF force field development” and shows Figure S1–S3 captions comparing QM and ReaxFF equations of state for crystalline LiOH, Li₂O, NaOH, Na₂O, CsOH, and Cs₂O. These plots document how the fitted potential reproduces pressure–volume or energy–volume behavior for ionic crystal phases used as training and validation targets during parameter optimization. The extract’s captions name each panel explicitly: crystalline equations of state for LiOH and Li₂O in Figure S1, NaOH and Na₂O in Figure S2, and CsOH and Cs₂O in Figure S3, each juxtaposing QM and ReaxFF curves as benchmarks for the electrolyte–water parameterization effort described in the parent article.

Methods

2 — Force-field training (SI: crystalline equation-of-state benchmarks). Section S1 documents ReaxFF development for alkali-hydroxide / oxide chemistry in the Fedkin J. Phys. Chem. A electrolyte–water line. The opening figures in the local SI PDF show P–V / energy–volume-style equations of state comparing QM and ReaxFF for LiOH/Li₂O (Fig. S1), NaOH/Na₂O (Fig. S2), and CsOH/Cs₂O (Fig. S3), used to anchor short-range ionic interactions in the broader fit. Molecular dynamics-based post-fit checks (if any) and any LAMMPS input decks are not the focus of this S1 head; see the parent 2019fedkin-j-phys-chem-development-reaxff for whether finite-T MD is reported there. DFT settings (functional, basis set, k-point mesh), ReaxFF optimization weights, and ParReaxFF / CMA-ES-style fitting workflow are reported in the parent article and the full SI—not in the short p1–2 extract in-repo.

1 — MD application (if ever applied to the trained FF): N/A on this SI ingest—no production NVT/NPT trajectory with stated box volume and ps-long equilibration is the focus of the S1 head; aqueous-MD validation (if any) is in the VOR JPCA text / SI 2019fedkin-j-phys-chem-development-reaxff, not on this slug. For blueprint N/A (indexed SI front only): System (atom count in a reported MD box): N/A; PBC / boundaries in a simulation cell: N/A; equilibration or production duration (ps/ns): N/A; timestep: N/A; NVT/NPT line in Figs. S1–S3 N/A—those are static equation-of- state (EOS) lattice sweeps (QM vs ReaxFF), not a trajectory log. Thermostat / barostat in time-dependent MD: N/A on this page. Temperature (K): N/A in the caption slices that only compare 0 K (or static T=0 lattice)–style EOS (see VOR for finite-T MD if any). P–V plots in Figs. S1–S3 document bulk crystal P–V for alkali oxides/hydroxides (training checks). External electric field: N/A**.

3 — DFT as a primary “Methods” narrative on this fragment page: N/A — use the parent article for full QM reproducibility; this entry only confirms which crystals enter the S1–S3 EOS plots.

Findings

The SI figures summarized in the extract indicate qualitative agreement between QM and ReaxFF equations of state for the listed alkali hydroxides and oxides, which underpins confidence in short-ranged ionic interactions within the broader Li/Na/Cs/O/H parameterization. Quantitative RMSE values, additional phases, and liquid-water benchmarks are in the full SI and main text; they are not exhaustively listed in normalized/extracts for this slug.

Limitations

extraction_quality: partial in the manifest: the local extract captures figure captions but not the entire SI. doi is empty in front matter here because the SI file is not a standalone DOI’d object; citations must use the parent article DOI. This is an SI package in the sense of NON_PRIMARY_ARTICLE_PAPER_SLUGS.md category A.

Confidence rationale: med—grounded on extract; full numerical claims require parent PDF.

Reader notes (navigation)