Crystal structure of the high pressure phase of PbI<sub>2</sub>
Bibliographic record
Abstract
The title compound has the layered CdCl2 (C6)-type structure under normal pressure. On compression, phase transition was found to take place at 0.5 GPa with a volume contraction of 4 % (Bridgman, 1948), but the structure of the high pressure phase has remained undetermined. We made X-ray diffraction measurements using powdered samples squeezed in a diamond-anvil cell at a pressure of 0.9 GPa on a synchrotron radiation source at Photon Factory. In the pattern taken using the radiation 0.06195 nm in wavelength, closely spaced 36 diffraction lines have been recorded up to 1/2d = 2.55 nm -1 . They could be indexed in terms of an orthorhombic unit cell of the sizes of a = 0.8419, b = 1.190 and c = 8.751 nm, the longest axis being parallel to the c-axis of the original CdCl2-type structure. Analysis of the pattern on the basis of the intensities of the diffraction lines has led to the structure that can be interpreted as being formed by collapsing thirteen layers of the CdCl2-type structure in the c-axis direction. It is denser by 10 % than that of the normal pressure phase in agreement with the P-V relation determined by Bridgman (1948). Discussion is given on the structural feature of the high pressure phase and suggestion to the possible structure model of phase which form on further compression of the compound.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.003 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".