Trends in the frequencies of ν(AsO <i> <sub> <i>x</i> </sub> </i> H <sub> <i>x</i> –1 </sub> ) [ <i>x</i> = 2–4] in selected As(V)-containing compounds investigated using quantum chemical calculations
Bibliographic record
Abstract
The application of computational chemistry to studies in geochemistry is increasingly becoming invaluable in explaining experimentally observed trends for surface interactions of pollutants with sorbents ubiquitous in the environment. We report computational results on factors that affect the force constant of AsO x bonds in As(V)-containing compounds relevant to geochemical environments. Geometries, atomic charges, and stretching frequencies of –AsO x H x–1 (x = 2– 4) moieties in these molecules were calculated using semi-empirical methods (PM3) and density functional theory (B3LYP) for both isolated (gas phase) molecules and hydrated complexes in which the molecules are surrounded by four water molecules. We found that the number of organic substituents has a relatively smaller effect on the force constant of AsO x bonds than protonation. The increase in resonance effect with deprotonation causes As–O bond lengths to increase, and the decrease in resonance in fully deprotonated species with increasing organic substitution causes As–O bond lengths to decrease. In the absence of the resonance effect in fully protonated species, As–O bond lengths increase with more organic substituents. Also, increasing organic substitution causes the charge on the central arsenic atom to decrease. Charges on oxygen atoms in As–OH bonds are more sensitive to deprotonation than to resonance relative to other oxygen atoms in As–O bonds. As expected, frequencies of ν(AsO x ) show an inverse relationship with As–O bond lengths upon deprotonation and organic substitution. Our results have implication for the interpretation of infrared and X-ray absorption spectra of adsorbed As(V)-containing compounds.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".