Structural Variations of Apatite Solid Solutions, Ca10(PO4)6(F,Cl,OH)2
Bibliographic record
Abstract
Apatite, Ca10(PO4)6(F,Cl,OH)2, is the most abundant phosphate mineral in the world with numerous uses in geology, materials science, biology, medicine, agriculture, and dentistry. The three main natural end members are fluorapatite (Ca10(PO4)6F2), chlorapatite (Ca10(PO4)6Cl2), and hydroxylapatite (Ca10(PO4)6OH2). Quantitative chemical compositions and backscattered electron (BSE) images on twenty-four natural apatite samples, from various locations, were obtained with an electron-probe microanalyzer (EPMA). Varying cation and anion content led to distinctive zoning and unique crystal features. Eight samples were selected and studied with synchrotron high-resolution powder X-ray diffraction (HRPXRD). All eight samples observed a hexagonal structure (P63/m), consisting of a phosphate tetrahedron, a Ca1 polyhedron, and a Ca2 polyhedron. The Ca1 site is a 9-coordinated system and the Ca2 site is a 6-coordinated with an addition anion containing either F, Cl and/or OH. Five of the seven samples were found to be single- phased fluorapatites with varying features and cation/anion content. Cation substitutions, such as Mn substituting for Ca in sample 1W2, reduces the cell parameters of apatite (a, c, V). Four samples displayed unique zoning (1V9, 1E9, SM and 1V5), however only 1E9 and SM were found to be multiphase apatites, with all phases being hexagonal in structure. Sample SM exhibited three phases - with fluorapatite being the primary phase along with 2 guest phases. Sample 1E9 displayed two separate phases of fluorapatite and hydroxylapatite, with the OH residing at 0.224 Å and F placed on the mirror planes at 0,0, 1⁄4.
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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) | 0.001 | 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".