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Supporting information: Development of the ReaxFF Reactive Force Field for Inherent Point Defects in the Si/Silica System

Evidence and attribution

Authority of statements

Prose sections below (Summary, Methods, Findings, etc.) are curated summaries of the publication identified by doi, title, and pdf_path in the front matter above. They are not new primary claims by this wiki.

For definitive numerical values, reaction schemes, and interpretations, use the peer-reviewed article (and optional records under normalized/papers/ when present)—not this page alone.

Summary

Corpus note: this slug indexes the J. Phys. Chem. A supporting-information PDF (papers/Nayir_JPC_C_SiOx_2019_SI.pdf) for the Si/silica defect ReaxFF article [[2019nayir-j-phys-chem-development-reaxff-2]]. The SI adds extra figures comparing QM and ReaxFF equations of state for Si and silica polymorphs, tabulated reaction energies for Si–O–H training sets, and implementation notes for ReaxFF, LAMMPS, or ADF. The main article redevelops Si/O/H parameters so that oxygen interstitials, migration in bulk Si, and a-SiO₂/Si interface oxidation treat point-defect physics omitted by earlier fits; the revised field (“ReaxFFpresent”) targets bond-centered O hopping with a barrier near ~65 kcal/mol, correcting SiOH(2010) behavior that had allowed spurious deep O diffusion near room temperature. The extract pages reproduced here show Figure S1 (EOS for α, β, cubic Si) and Figure S2 (cristobalite and coesite silica polymorphs) with paired QM/ReaxFF curves, plus Table S1 listing Si–O–H reaction energies in kcal mol\(^{-1}\) for dimer/trimer anion condensation steps used in the fit.

Methods

Document role. This PDF is the Supporting Information for the Si/silica defect ReaxFF work; full simulation protocols and the main ReaxFF optimization narrative are in [[2019nayir-j-phys-chem-development-reaxff-2]].

1 — MD application (production / validation runs). N/A in this SI slice for a full engine / ensemble / timestep / thermostat table: the indexed SI material stresses supplemental QM vs ReaxFF EOS plots (Figure S1 for α-, β-, and cubic Si; Figure S2 for cristobalite and coesite) and Table S1 reaction energies, not a reproduced LAMMPS run log. Barostat, electric field, shear/shock, enhanced sampling: N/A in the SI content summarized here; O migration and interface MD are in the main article.

2 — Force-field training (ReaxFF, Si/O/H). The ReaxFFpresent refit corrects SiOH(2010) O superdiffusion; the main text cites bond-centered O hopping with a barrier on the order of ~65 kcal/mol (see main paper). Table S1 lists ReaxFFpresent vs DFT (kcal mol\(^{-1}\)) for Si–O–H condensation training reactions (dimer/trimer anion and related steps). The SI states compatibility of the parameter set with ReaxFF in LAMMPS and ADF. QM functional / basis and the CMA-ES fit details are in the main article.

3 — Static QM (SI validation). Figure S1–S2 pair DFT and ReaxFF EOS for Si and silica polymorphs; DFT settings follow the main paper.

4 — Review / non-simulation. N/A.

MD protocol line items (SI honesty). Full production MD with reported atom counts, 3D PBC, NVT or NPT ensemble, timestep in fs, equilibration and production ns spans, thermostat, and any barostat / hydrostatic pressure control are N/A in this SI PDF slice—see the main article ([[2019nayir-j-phys-chem-development-reaxff-2]]) for those LAMMPS/ADF reactive MD details.

Findings

Extended QM vs ReaxFF numerical agreement plots and tabular training targets support reproducibility; substantive mechanistic conclusions (O migration pathways, interface transport) belong with the main text at the same DOI. Representative Table S1 entries in the extract span −14 to −28 kcal mol\(^{-1}\) depending on reaction, illustrating how the refit balances clustered Si(OH)\(_x\) reactions against DFT references; readers should treat these numbers as SI training diagnostics, not standalone mechanistic claims without the main article’s discussion of defect migration barriers and interface oxidation tests.

Limitations

SI-only packaging does not replace the main article narrative; cite [[2019nayir-j-phys-chem-development-reaxff-2]] for interpretation.

Relevance to group

Provenance bundle for the Si/O/H ReaxFF reparameterization used in follow-on silica and interface studies.

Citations and evidence anchors

Pair with papers/Nayir_JPC_C_SiOx_2019.pdf (main article). SI hosted with https://doi.org/10.1021/acs.jpca.9b01481