THE UNIQUE CASE OF TIN(II) FLUORIDE CONTAINING UNEXPECTED SUBSTITUTIONAL SOLID SOLUTIONS: LOCAL STRUCTURE VERSUS GLOBAL STRUCTURE
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Bibliographic record
Abstract
Solid solutions provide the means of tailoring the properties of materials by adjusting their chemical composition without phase demixing. A solid solution is a compound with a variable composition. Substitutional solid solutions are formed by replacing some atoms/ions by other atoms/ions. In order to be energetically favored, this replacement is possible only if certain criteria are met: (1) size criterion: there should be no more than 15% difference between the radius of the atoms/ions that are replacing each other, and (2) bonding type criterion: the replacing atom/ion should be able to accept the bonding type of the host. If these criteria are not met, the substitution will create an unacceptable level of stress at and around the substitution sites. In our studies of the SnF2/MF2 systems, where (M = Ca, Sr, Ba or Pb), we have found a M1-xSnxF2 solid solution for M = Ca and Pb, with a wide range of composition in the case of Pb. In addition, the investigation of the SnF2/MF2/MCl2 systems revealed an even more complicated type of solid solution. All should be forbidden according to accepted criteria: the alkaline earth metal fluorides and chlorides have ionic structures, while SnF2 has three allotropes, all which are characterized by strongly covalent bonding with a significant amount of polymerization. In addition, the similar size criterion is grossly violated, Sn 2+ being much smaller than the alkaline earth metal, well beyond the accepted limit of about 15% for ion substitution. Furthermore, the wider solid solutions are formed with PbF2 and BaClF, i.e. for the cations that have the largest size difference. The Ba1-xSnxCl1+yF1-y solid solution is by far the most unusual, and it is probably unique since it is a doubly disordered solid solution (simultaneous disorder on the cationic sita and on the anionic sites). The combined use of X-ray diffraction and Mssbauer spectroscopy was necessary in order to understand these solid solutions.
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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 | 0.000 | 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 | 0.003 | 0.001 |
| 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 it