Probing atomic-scale processes at the ferrihydrite-water interface with reactive molecular dynamics
Bibliographic record
Abstract
Interfacial processes involving metal (oxyhydr)oxide phases often control the mobility and bioavailability of nutrient and contaminant elements in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy, to derive accurate surface complexation model constants for ferrihydrite-water systems containing aqueous \ce{MoO_4^{2-}}. This is achieved by employing a force-field that is adept at capturing the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption processes or proton transfer events. We inform surface complexation models by exploring the free energy landscape of \ce{MoO_4^{2-}} adsorption at the ferrihydrite-water interface at different concentrations. We find how hydration and adsorption induce changes in surface charge, prompting the surface to restructure into more disordered ferrihydrite phases. We observe how the dynamics of adsorbed complexes are concentration-dependent and how surface restructuration, along with adsorption, influence the interfacial hydrogen bond network. By incorporating reactivity, reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".