Raman Scattering Studies of the Structural Phase Transitions in Single-Crystalline CH<sub>3</sub>NH<sub>3</sub>PbCl<sub>3</sub>
Bibliographic record
Abstract
Methylammonium lead trihalide perovskites CH 3 NH 3 PbX 3 (X = Cl, Br, and I) have recently attracted huge attention as a promising candidate for highly efficient solar cell absorber materials. To understand the physical properties of halide perovskites, we investigated the CH 3 NH 3 PbCl 3 single crystal by Raman scattering spectroscopy from 80 K to room temperature. Benchmarking the phonon modes and their Raman activities obtained by density functional calculations, we successfully assign the molecular vibrations of methylammonium in the frequency range from 400 to 3300 cm –1 . In the temperature-dependent Raman scattering spectra, the internal vibrational modes of the CH 3 NH 3 + cation are observed in the frequency range above 400 cm –1 and a number of peaks among them show characteristic changes that reflect the phase transition occurring at about 160 K in CH 3 NH 3 PbCl 3 . A noticeable Raman peak at 2900 cm –1 persists in a wide range of temperature, suggesting the existence of microcrystalline methylammonium chloride possibly left on the crystal surface from the growth process or spontaneously formed after synthesis.
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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) | 0.001 | 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 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".