Slip Mechanisms of Hydroxylated α-Al<sub>2</sub>O<sub>3</sub> (0001)/(0001) Interfaces: A First-Principles Molecular Dynamics Study
Bibliographic record
Abstract
First-principles molecular dynamics simulations are used to explore sliding along interfaces composed of different forms of hydroxylated (0001)/(0001) interfaces of α-alumina (Al 2 O 3 ). The results demonstrate that a fully hydroxylated form of the interface is insensitive to changes in normal pressure, P . Meanwhile, partially hydroxylated interfaces undergo changes in structure when P is increased. The different interface structures exhibit different sliding mechanisms. The fully hydroxylated interface exhibits smooth sliding with low critical shear stresses. At low P, the partially hydroxylated interface takes part in a slip mechanism that is dominated by changes in hydrogen bonding across the interface, leading to larger critical shear stresses than observed for the fully hydroxylated system. At high P, the partially hydroxylated interface undergoes slip through a process involving the formation and dissociation of Al−O bonds across the interface, leading to high critical shear stresses and irreversibly changing the interface structure. The differences in the slip mechanisms for these systems are rationalized in terms of the electronic structures of the interfaces. As a whole, the study provides detailed insight regarding the relationship between interface structure, friction, and wear, and highlights the importance of fully chemically passivating surfaces to minimize friction and wear.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".