SINGLE-CRYSTAL EPR STUDY OF Fe3+ AND VO2+ IN PREHNITE FROM THE JEFFREY MINE, ASBESTOS, QUEBEC
Bibliographic record
Abstract
Prehnite from the Jeffrey mine, in Asbestos, Quebec, has been investigated by optical microscopy, electron-microprobe analysis, single-crystal X-ray-diffraction (XRD) analysis, and electron paramagnetic resonance (EPR) spectroscopy. Electron-microprobe analyses yield an average iron content of 0.053(34) wt% Fe 2 O 3 ; single-crystal XRD intensity datasets confirm the space group P 2 cm . Single-crystal EPR spectra measured from 290 to 13 K reveal at least six paramagnetic defects: three Fe 3+ centers, a VO 2+ radical, a Mn 2+ center, and an Al-associated O − center. Spin-Hamiltonian parameters of the VO 2+ radical show that it resides at an octahedral site and most likely originated from a V 3+ O 4 (OH) 2 octahedron by removal of a proton and trapping of a hole to form a covalent V=O bond during natural radiation. Spin-Hamiltonian parameters, including the high-spin terms of type S 4 , BS 3 and BS 5 , for the dominant Fe 3+ center also show it to reside at an octahedral site. Two less abundant Fe 3+ centers have similar orientations in effective principal axes of g, indicative of occupancies at the octahedral site as well. Their differences in effective principal values of g may be attributed to different degrees of local distortion of the octahedral site. A previous interpretation of the powder EPR spectra for two Fe 3+ sites in prehnite has been shown to be incorrect. Spin-Hamiltonian parameters for Fe 3+ in prehnite have wide implications for interpretation of EPR spectra of Fe 3+ in layer silicates.
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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 | 0.001 | 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".