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: FeAsO 4 ·2H 2 O AlAsO 4 ·2H 2 O, GaAsO 4 ·2H 2 O, and InAsO 4 ·2H 2 O are reported. In particular, upon comparison of FeAsO 4 ·2H 2 O to AlAsO 4 ·2H 2 O, 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 ν 1 (AsO 4 3− ) 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 FeAsO 4 ·2H 2 O (lowest) < InAsO 4 ·2H 2 O < GaAsO 4 ·2H 2 O < AlAsO 4 ·2H 2 O (highest); this order also followed exactly the measured arsenic release of these phases. This shift in ν 1 (AsO 4 3− ) position was rationalized to stem from the differences in the electronegativities of the M 3+ cations. The trends mentioned above were verified and found to also hold for the isostructural phosphate analogues strengite (FePO 4 ·2H 2 O) and variscite (AlPO 4 ·2H 2 O) 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 M 3+ cation in these isostructural phases and their stability (As or P release) in water. Copyright © 2010 John Wiley & Sons, Ltd.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| 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".