Reactive dynamics simulation of monolayer and multilayer adsorption of glycine on Cu(110)
Evidence and attribution¶
Authority of statements
Sections below summarize the publication identified by doi, title, and pdf_path in the front matter.
Summary¶
The interaction of glycine with metal surfaces couples surface coordination chemistry with hydrogen-bond networks in two-dimensional adlayers. This Journal of Physical Chemistry C article uses ReaxFF reactive molecular dynamics to follow neutral gas-phase glycine impinging on Cu(110) across mono- and multilayer coverages. Reactive trajectories permit deprotonation, zwitterionic-like arrangements, and diffusion-mediated ordering over nanosecond-scale runs, capturing pathways that static single-configuration DFT would omit. The authors relate their structural motifs to experimental and theoretical literature on amino-acid ordering on copper, emphasizing how coverage modulates binding denticity and long-range chirality patterns. The 2013 JPCC study complements the companion Langmuir article on glycine and diglycine spectroscopy on Cu(110) by prioritizing dynamical pathways over static cluster models. Together, these papers illustrate when reactive MD is necessary for amino acids because proton transfers and H-bond networks fluctuate on simulation time scales accessible to ReaxFF but not to single-point DFT alone.
Methods¶
Engine / reactive model: ReaxFF reactive molecular dynamics as implemented in the authors’ workflow (see article for code and timestep), with bond-order updates each integration step so carboxyl deprotonation, interlayer proton transfer, and diffusion can occur without preset reaction templates.
System: Cu(110) slabs with in-plane periodic boundary conditions; neutral gas-phase glycine starting structures evolve toward anionic glycinate-like motifs as summarized in the abstract. Mono- vs multilayer regimes are distinguished by coverage in the simulation protocol described in the paper.
Thermodynamics / stages: Equilibration and production segments use the thermostatting and duration choices stated in J. Phys. Chem. C (full numerical table not reproduced in the short extract; consult papers/ReaxFF_others/Monti_Glycine_CuO_JPC_2013.pdf for timestep, ensemble, and total simulated time).
Analysis: Radial distribution functions, coordination metrics, and denticity classification (bidentate vs tridentate) versus coverage follow the Results procedures; the abstract highlights ~2 Å average Cu–O/N distances for the most stable motifs identified.
MD slots not in p1–2 extract: N/A — literal LAMMPS-level integration settings, supercell atom totals, full 3D periodic cell vectors, whether NPT pressure coupling or constant-volume NVT/NVE legs are used for each stage, target temperature windows beyond the abstract’s qualitative thermalization language, Berendsen/Nosé–Hoover-class thermostat parameters, electric fields, and enhanced sampling are not quoted from normalized/extracts/2013monti-venue-research_p1-2.txt; confirm in papers/ReaxFF_others/Monti_Glycine_CuO_JPC_2013.pdf.
2 — Force-field training: N/A — employs literature ReaxFF for glycine–Cu chemistry.
3 — Static QM / DFT-only: N/A — primary evidence is reactive MD trajectories plus literature comparisons.
Findings¶
Outcomes and mechanisms: Chemisorbed arrangements that deprotonate the carboxyl and transfer protons to second-layer molecules are among the most stable motifs identified, with carboxyl oxygens and amino nitrogens near Cu at roughly 2 Å average distances (abstract). Adsorption proceeds through multistep pathways with intermediate coordination states.
Comparisons: Low coverage favors bidentate-like attachment, whereas higher coverage yields long-range ordered heterochiral domains where tridentate motifs become prominent, consistent with the literature survey embedded in the paper. Reactive trajectories connect kinetic accessibility of zwitterionic-like states to long-range packing, which fixed-composition energy minimizations would miss.
Sensitivity / design levers: Coverage modulates denticity and chiral ordering; nanosecond-scale runs place the model in a regime where surface diffusion and reordering compete with desorption for the finite cells used.
Limitations and outlook: ReaxFF parameters for amino acids on transition metals should be checked against DFT for quantitative energetics; impingement protocols may differ from slow dosing experiments.
Corpus honesty: Companion spectroscopy/diglycine study: [[2013monti-venue-la-2013-01746d]].
Limitations¶
ReaxFF parameters for amino acids on transition metals should be checked against DFT for quantitative energetics; finite system sizes may alter chiral domain sizes. Impingement protocols in MD may differ from molecular beam experiments dosing glycine slowly. Thermal equilibration assumptions should match the article when reproducing coverage-dependent ordering.