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
Notice bibliographique
Résumé
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 + .
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,002 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».