The crystal structure of comancheite, Hg<sup>2+</sup><sub>55</sub>N<sup>3–</sup><sub>24</sub> (OH,NH<sub>2</sub>)<sub>4</sub>(Cl,Br)<sub>34</sub>, and crystal-chemical and spectroscopic discrimination of N<sup>3–</sup> and O<sup>2–</sup> anions in Hg<sup>2+</sup> compounds
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Bibliographic record
Abstract
Abstract The crystal structure of comancheite, Hg 2+ 55 N 3– 24 (OH, NH 2 ) 4 (Cl,Br) 34 , orthorhombic, space group Pnnm , a = 18.414(5), b = 21.328(6), c = 6.6976(19) Å, V = 2630(2) Å 3 , Z = 1, was solved by direct methods and refined to an R 1 index of 4.3% based on 4160 unique observed reflections. In the structure of comancheite, there are nine crystallographically distinct Hg 2+ cations, each of which is coordinated by two N 3– anions to form near-linear N 3– –Hg 2+ –N 3– groups. Four other crystallographically distinct Hg 2+ cations are coordinated by a mixture of N 3– , O 2– , (OH) – and (NH 2 ) – anions, and there is a small amount of [Hg–Hg] 2+ dimer. In addition, there are eight crystallographically distinct halogen sites, three of which are completely occupied by Cl – , and five of which are occupied by both Cl – and Br – . The principal anion, N 3– , shows a strong preference for tetrahedral coordination by Hg 2+ , which results in a strongly bonded three-dimensional {–Hg 2+ –N 3– –} framework. This framework is both interrupted and contains large interstices that incorporate additional Hg 2+ cations, a very small amount of [Hg+–Hg+] 2+ dimer and additional anion species, O 2– , (OH) – and (NH 2 ) – , that coordinate Hg 2+ . Comancheite was described originally as an Hg-oxide mineral. The major change in chemical composition indicated by the present work was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (Voting Proposal 13-B). The presence of N provides some analytical challenges, particularly in the presence of Hg. New bond-valence parameters were derived for Hg 2+ –N 3– bonds [R o (N 3– ) = 1.95] using well refined Hg 2+ structures, and this allows discrimination between Hg 2+ –O 2– and Hg 2+ –N 3– bonds based on the valence-sum rule. Comparison of the Raman spectra of several Hg-bearing minerals shows that peaks in the range 500–700 cm –1 are characteristic of Hg 2+ –N 3– stretching vibrations whereas peaks in the range 350–500 cm –1 are characteristic of Hg 2+ –O 2– stretching vibrations; Hg 2+ –O 2– and Hg 2+ – N 3– bonds may be discriminated on this basis.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.004 | 0.003 |
| Meta-epidemiology (broad) | 0.005 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.000 | 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