Raman spectroscopic study of the hydrogen and arsenate bonding environment in isostructural synthetic arsenates of the variscite group—M<sup>3+</sup> AsO<sub>4</sub>·2H<sub>2</sub>O (M<sup>3+</sup> = Fe, Al, In and Ga): implications for arsenic release in water
Bibliographic record
Abstract
Abstract The Raman spectra of synthetic compounds equivalent to the variscite group: FeAsO4·2H2O AlAsO4·2H2O, GaAsO4·2H2O, and InAsO4·2H2O are reported. In particular, upon comparison of FeAsO4·2H2O to AlAsO4·2H2O, it is observed that the Type II (weak) H‐bond lengths in the latter are slightly longer, which is postulated to affect the stability (As release) in water at pH 5 and 7. Arsenate stretching and bending vibrations were found to be distinct in terms of spectral structure and therefore well suited for fingerprinting. The calculated AsO bond strengths from existing crystallographic data showed no significant variations. The strongest ν1 (AsO43−) stretch was used to monitor the AsO bonding interactions in the four AsOM units, where a shift of 114 cm−1 was observed in the order FeAsO4·2H2O (lowest) < InAsO4·2H2O < GaAsO4·2H2O < AlAsO4·2H2O (highest); this order also followed exactly the measured arsenic release of these phases. This shift in ν1 (AsO43−) position was rationalized to stem from the differences in the electronegativities of the M3+ cations. The trends mentioned above were verified and found to also hold for the isostructural phosphate analogues strengite (FePO4·2H2O) and variscite (AlPO4·2H2O) using published data. Therefore, it is postulated that, as observed with the stability of solution complexes, there may be a correlation between the electronegativity of the M3+ cation in these isostructural phases and their stability (As or P release) in water. Copyright © 2010 John Wiley & Sons, Ltd.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".