THE CRYSTAL CHEMISTRY OF FAIZIEVITE, K2 Li6 Na (Ca6Na) Ti4 [Si6O18]2 [Si12O30] F2, A NOVEL STRUCTURE BASED ON INTERCALATED BLOCKS OF THE BARATOVITE AND BEREZANSKITE STRUCTURES
Bibliographic record
Abstract
The crystal structure of faizievite, ideally K 2 Li 6 Na (Ca 6 Na) Ti 4 [Si 6 O 18 ] 2 [Si 12 O 30 ] F 2 , a 9.8156(9), b 9.8249(9), c 17.3087(16) A, α 99.209(2), β 94.670(2), γ 119.839(1)°, V 1403.7(4) A 3 , space group P 1, Z = 1, D calc. 2.846 g/cm 3 , has been solved and refined to an R 1 index of 7.5% based on 5044 unique ( F 0 > 4σ F ) reflections collected on a Bruker single-crystal P 4 diffractometer with a 4K CCD detector and Mo K α X-radiation. Electron-microprobe analysis gave SiO 2 60.65, TiO 2 13.44, Nb 2 O 5 0.11, CaO 14.52, K 2 O 3.93, Na 2 O 1.99, SrO 0.72, Rb 2 O 0.13, F 1.30, Li 2 O 3.76, sum 100.24 wt.%. Concentrations of Li 2 O, Rb 2 O, SrO and BaO were determined by ICP–OES. There are fifteen tetrahedrally coordinated sites: twelve sites are occupied by Si, with a grand Si –O> of 1.613 A; three sites are occupied by Li, with a grand Li –O> distance of 1.928 A. There are six octahedrally coordinated sites. The two Ti (1) and Ti (2) sites are occupied by Ti 2.00 with Ti –O> = 1.937 and 1.934 A, respectively. The four M sites are occupied by Ca with minor Sr and Na: the M (1) site (= Ca 2.00 ), with M (1)–O> = 2.441 A, the M (2) site [= (Ca 1.87 Sr 0.13 )], with M (2)–O> = 2.424 A, the M (3) site [= (Ca 1.56 Na 0.40 Sr 0.04 )], with M (3)–O> = 2.415 A, and the M (4) site [= (Ca 0.73 Na 0.27 )], with M (4)–O> = 2.418 A. There are two interstitial A sites: the A (1) site is [12]-coordinated and is occupied by (K 1.93 Ba 0.04 Rb 0.03 ), with A (1)–O> = 3.092 A; the A (2) site is [9]-coordinated and is occupied by (Na 0.86 □ 0.14 ), with A (2)–O> = 2.718 A. The crystal structure of faizievite consists of four types of (001) sheets. The Si tetrahedra form two types of six-membered rings: a single (Si 6 O 18 ) ring, as in baratovite, and a double (Si 12 O 30 ) ring, as in milarite-group minerals, in the ratio 2:1. Each type of ring forms a distinct sheet (Na atoms occur in a sheet of milarite double rings). Two other sheets are: a sheet of corner-sharing (LiO 4 ) tetrahedra and (TiO 6 ) octahedra with K atoms in large voids, and a sheet of edge-sharing M octahedra ( M = Ca >> Na). Each sheet is characterized by a planar cell based on translation vectors, t 1 and t 2 , with t 1 ≈ t 2 ≈ 9.8 A and t 1 ∧ t 2 close to 120°. The composition of the four individual sheets within the planar cell t 1 , t 2 is: (1) (Si 6 O 18 ), (2) (Si 12 O 30 )Na, (3) KLi 3 Ti 2 , (4) (Ca 6 Na)F 2 . The crystal structure of faizievite is a hybrid of the structures of baratovite, KLi 3 Ca 7 Ti 2 (Si 6 O 18 ) 2 F 2 , and berezanskite, KLi 3 Ti 2 (Si 12 O 30 ) (milarite group). The baratovite block of composition [KLi 3 (Ca 6 Na)Ti 2 (Si 6 O 18 ) 2 F 2 ] comprises sheets (3)(1)(4)(1). The berezanskite block of composition [KNaLi 3 Ti 2 (Si 12 O 30 )] comprises sheets (3)(2). In the faizievite structure, baratovite and berezanskite blocks alternate along [001] and sum to the following sequence: (3)(1)(4)(1)(3)(2). There are minor differences between the chemical compositions of baratovite and berezanskite and analogous blocks in the crystal structure of faizievite. Baratovite, K Li 3 Ca 7 Ti 2 (Si 6 O 18 ) 2 F 2 , and the baratovite block in faizievite, KLi 3 (Ca 6 Na)Ti 2 (Si 6 O 18 ) 2 F 2 , are related by the substitution: [6] Ca 2+ ⇔ [6] Na + . Berezanskite, K [9] □ Li 3 Ti 2 (Si 12 O 30 ), and the berezanskite block in faizievite, K [9] NaLi 3 Ti 2 (Si 12 O 30 ), are related by the substitution: [9] □ ⇔ [9] Na + . Assembly of faizievite from baratovite and berezanskite components is accompanied by the following substitution: [6] Ca 2+ + [9] □ ⇔ [6] Na + + [9] Na + .
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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 | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".