Skip to content

ReaxFF molecular dynamics study on the influence of temperature on adsorption, desorption, and decomposition at the acetic acid/water/ZnO(101̄0) interface enabling cold sintering

Summary

Cold sintering enables densification of ceramics at dramatically lower temperatures by exploiting transient solvent chemistry at particle contacts; acetic acid and water mixtures are common processing fluids for ZnO-rich systems. This ACS Appl. Mater. Interfaces article uses ReaxFF MD of acetic acid + water on ZnO(10\(\bar{1}\)0) to map how temperature modulates adsorption, desorption, and decomposition channels relevant to interfacial transport during sintering. The narrative highlights two deprotonation pathways: to terminal Zn-associated sites (terminal hydroxyl formation) and to bridging hydroxyls with associated water release, and it compares coverage trends with Langmuir-like expectations. Acetate decomposition toward CO\(_2\) (and CH\(_2\)O among smaller products) is discussed in connection with literature behavior on ZnO. The corpus PDF is a proof; confirm final labels in the publisher version when available.

Methods

A — Force-field assembly / validation

  • Combination model: H/O/Zn block from prior water/ZnO ReaxFF (ref. 34 in the ACS AMI article) merged with C/H/O organics parameters, plus additional optimization for acetic acid/acetate interactions with ZnO (§2.1 ReaxFF validation in the paper).
  • Validation narrative: §2.1 explains how the merged potential is tested against expected adsorption/dissociation behavior for the acetic acid/water/ZnO interface (see article for benchmarks and any literature DFT comparators).

B — Reactive MD (acetic acid / water on ZnO(10\(\bar{1}\)0))

LAMMPS ReaxFF MD places acetic acid + water on a ZnO(10\(\bar{1}\)0) slab while sweeping temperature across the range reported in §2 to separate adsorption-limited and decomposition-limited regimes. Slab cells use in-plane periodic boundary conditions with vacuum along the surface normal. Production trajectories use the NVT ensemble with a femtosecond integration timestep and Nose–Hoover or Berendsen thermal control as listed in Methods/SI; equilibration plus production segments long enough to accumulate coverage statistics at each \(T\) appear in the article tables (ps/ns). Barostat: N/A — no hydrostatic NPT control for the cited slab temperature sweeps unless the SI documents an exception. Electrostatics follow standard ReaxFF Coulomb/vdW with QEq-class charges and LAMMPS PPPM/cutoff settings given in §2. Electric field / enhanced sampling: N/A — not used.

C — Analysis

Simulated coverages of acetate, molecular water, terminal/bridging hydroxyls, and gas-phase products are compared to Langmuir-like expectations and to literature MD/experiment on ZnO carboxylates.

Findings

Outcomes and mechanisms

With increasing temperature, acetic acid dissociation and acetate adsorption strengthen first, then acetate coverage falls via desorption or decomposition at higher \(T\). Acetate decomposition is described as nucleophilic O attack on the methyl carbon, yielding CO\(_2\), consistent with experimental reports cited in the paper. Molecular water and bridging hydroxyl coverages decline on heating in line with prior MD trends referenced there; at elevated \(T\), acetate remains on the surface longer than water or bridging hydroxyls under the reported conditions.

Comparisons and processing relevance

The authors relate the temperature-dependent adsorption/decomposition balance to cold sintering process design on ZnO, treating ReaxFF as a qualitative solvent-screening tool rather than a universal oxide–solvent model.

Sensitivity

Temperature is the primary knob separating adsorption-limited vs reaction-limited surface chemistry in the simulations.

Limitations and corpus honesty

The corpus pdf_path is an ACS proof; confirm final figure labels and any additional gas-phase products in the version-of-record PDF.

Limitations

Proof PDF; confirm final figure labels and any additional products in the published article.

Relevance to group

van Duin coauthored application of ReaxFF to ZnO processing interfaces tied to cold sintering technology.

Citations and evidence anchors