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Water-mediated surface diffusion mechanism enabling the Cold Sintering Process: a combined computational and experimental study

Summary

This slug registers an Angewandte Chemie Accepted Article PDF (SENGUL_et_al-2019-Angewandte_Chemie_International_Edition.pdf) for the same communication as [[2019sengul-venue-water-mediated]], DOI 10.1002/anie.201904738. The work combines cold sintering process (CSP) experiments on ZnO with ReaxFF molecular dynamics to explain fast grain growth at low temperature. The abstract argues that CSP densifies ceramics at temperatures far below conventional sintering; for ZnO, grain growth kinetics show reduced activation energies, and the atomistic mechanism is investigated with simulations. Zinc cation recrystallization under acidic conditions is examined; adsorption of Zn²⁺ to surfaces can be rate-limiting. Surface hydroxylation under CSP is found not to freeze crystallization—instead, hydroxylation forms surface complexes that accelerate surface diffusion by orders of magnitude, speeding recrystallization. The Accepted Article may differ in layout from the final Version of Record; use the water-mediated sibling when matching pagination to citations. The communication emphasizes sustainable processing motivations for low-temperature ceramic densification and cites breadth of CSP applicability across many inorganic systems in the opening paragraphs—those survey claims are part of the published framing and should be read alongside the ZnO-specific simulation evidence in the same paper.

Methods

Experiments: CSP densification / grain growth measurements for ZnO under conditions described in the paper and SI.

ReaxFF MD: Molecular dynamics in LAMMPS for ReaxFF (see the VOR on [[2019sengul-venue-water-mediated]] for the exact package string). ZnO slabs in 3D PBC with water and acid-related species; NVT or NPT ensemble; Nose–Hoover-class thermostat; timestep 0.1–0.5 fs; equilibration and production ps–ns in the SI; ~10³-scale atoms; ~300 K and other temperatures in K as in the VOR. Hydrostatic pressure with NPT Parrinello–Rahman barostat is N/A to re-specify on this duplicate PDF—use the VOR / ** SI for bar targets. External E-field, shear, umbrella: N/A if unstated. 2 — ReaxFF reparameterization: N/A. This slug is a hash-level Accepted Article duplicate** only.

Findings

Surface-mediated diffusion is central to the proposed CSP mechanism: hydroxylation correlates with large increases in modeled surface mobility, consistent with accelerated grain growth relative to conventional sintering. Zn surface chemistry under acidic pathways can be kinetically limiting. Full quantitative barriers and figures should be taken from the VOR or the primary wiki page when figures differ between PDFs.

Limitations

Accepted Article text may not match final proofreading. Models focus on ZnO; other CSP chemistries need separate validation. ReaxFF surface chemistry is parametrization-dependent; compare DFT benchmarks or experimental grain-growth exponents when available before exporting barrier values into wider sintering databases. Keep SI structures and simulation cells as the authoritative numerical reference for MD reproduction.

Relevance to group

Core oxide / sintering ReaxFF contribution with experimental validation (van Duin co-author).

Citations and evidence anchors

Reader notes (navigation)