From structure topology to chemical composition. IX. Titanium silicates: revision of the crystal chemistry of lomonosovite and murmanite, Group-IV minerals
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Bibliographic record
Abstract
Abstract The crystal structures of lomonosovite, ideally Na 10 Ti 4 (Si 2 O 7 ) 2 (PO 4 ) 2 O 4 , a = 5.4170(7) Å, b = 7.1190(9) Å, c = 14.487(2) Å, a = 99.957(3)°, β = 96.711(3)°, γ = 90.360(3)°, V= 546.28(4) Å 3 , D calc . = 3.175 g cm“ 3 , and murmanite, ideally Na 4 Ti 4 (Si 2 O 7 ) 2 O 4 (H 2 O) 4 , a = 5.3875(6) Å, b = 7.0579(7) Å, c = 12.176(1) Å, a = 93.511(2)°, 0 = 107.943(4)°, y = 90.093(2)°, V = 439.55(2) Å 3 , D calc . = 2.956 g.cm∼ 3 , from the Lovozero alkaline massif, Kola Peninsula, Russia, have been refined in the space group P1̄ (Z = 1) to R values of 2.64 and 4.47%, respectively, using 4572 and 2222 observed |F ° ≥ 4σF| reflections collected with a single-crystal Bruker AXS SMART APEX diffractometer with a CCD detector and Mo-Kα. radiation. Electron microprobe analysis gave empirical formulae for lomonosovite (Na 9.50 Mn 0.16 Ca 0.11 ) Σ9.77 (Ti 4+ 2.83 Nb 0.51 Mn 0.27 2+ Zr 0.11 Mg 0.11 Fe 2+ 0.10 Fe 3+ 0.06 Ta 0.01 ) Σ4.00 (Si 2.02 O 7 ) 2 (P 0.98 O 4 ) 2 (O 3.50 F 0.50 ) Σ4 , Z = 1, calculated on the basis of 22(O+F) a.p.f.u., with H 2 O determined from structure refinement and Fe 3+ /(Fe 2+ +Fe 3+ ) ratios obtained by Mössbauer spectroscopy. The crystal structures of lomonosovite and murmanite are a combination of a titanium silicate (TS) block and an intermediate (I) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is characterized by a planar cell based on translation vectors, t 1 and t 2 , with t 1 \ ∼5.5 and t 2 ∼7 Å and t t A t 2 close to 90°. The TS block exhibits linkage and stereochemistry typical for Group IV (Ti = 4 a.p.f.u.) of the Ti disilicate minerals: two H sheets connect to the O sheet such that two (Si 2 O 7 ) groups link to Ti polyhedra of the O sheet adjacent along t x . In murmanite and lomonosovite, the invariant part of the TS block is of composition Na 4 Ti 4 (Si 2 O 7 ) 2 O 4 . There is no evidence of vacancy-dominant cation sites or (OH) groups in the O sheet of lomonosovite or murmanite. In lomonosovite, the I block is a framework of Na polyhedra and P tetrahedra which gives 2[Na 3 (PO) 4 ] p.f.u. In murmanite, there are four (H 2 O) groups in the intermediate space between TS blocks. In lomonosovite, TS and I blocks alternate along c. In murmanite, TS blocks are connected via hydrogen bonding. The H atoms were located and details of the hydrogen bonding are discussed.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
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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 it