Crystal structure determination of kosnarite, KZr2(PO4)3, from the Mario Pinto Mine, Jenipapo district, Itinga, Brazil
Bibliographic record
Abstract
ABSTRACT The crystal structure of a natural kosnarite, KZr2(PO4)3 from the Mario Pinto Mine, Jenipapo district, Brazil, has been determined for the first time. Kosnarite and its related synthetic compounds (NZP) are open-framework orthophosphates of the type ([6]M′[8]M′′)L2(TO4)3 (where M = Li, Na, K, Rb, Cs; L = Ti, Zr, Hf; and T = P, Si). These compounds have been proposed as potential radioactive waste hosts as a result of their physiochemical properties and because their crystal structure allows for extreme isomorphism and incorporation of all 42 radioactive nuclides present in nuclear waste. Kosnarite from the Mario Pinto mine is hexagonal, Rc, with a = 8.7205(1), c = 23.9436(3) Å, and V = 1576.89(4) Å3. The average chemical formula (n = 75) is (K0.96Na0.02)Σ0.98(Zr1.93Hf0.08)Σ1.01(P2.99Si0.01)Σ3.00O12. The structure contains one six-coordinated Zr site (L), one four-coordinated P site (T), and a six-coordinated K site (M′); in kosnarite, the M″ site is vacant. The average bond lengths in the ZrO6 octahedra (2.0646 Å) and PO4 tetrahedra (1.5278 Å) are slightly larger than those observed in the synthetic analogue (<Zr–O> = 2.063 Å, <P–O> = 1.522 Å). The ZrO6 octahedra and PO4 tetrahedra share corners to form ribbons of [Zr2(PO4)3]– units parallel to the c axis, which are further joined by PO4 tetrahedra perpendicular to c to form a 3D network. Kosnarite is one of only five natural alkali zircono-orthophosphates, all of which are late-stage hydrothermal minerals. Although synthetic Na-dominant endmember analogues of kosnarite exist, the distortions in the structure with respect to the M and L octahedra, along with experimental evidence at hydrothermal temperatures, suggest that only K (or Li) endmembers are possible in nature.
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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 | 0.000 | 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 | 0.001 | 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 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".