Uncovering Halogen Mixing and Octahedral Dynamics in Cs <sub>2</sub> SnX <sub>6</sub> by Multinuclear Magnetic Resonance Spectroscopy
Bibliographic record
Abstract
Cs 2 SnX 6 (X = Cl, Br, and I) compounds have emerged as promising lead-free and ambient-stable materials for photovoltaic and optoelectronic applications. To advance these promising materials, it is crucial to determine the correlations between physical properties and their local structure and dynamics. Solid-state NMR spectroscopy of multiple NMR-active nuclei ( 133 Cs, 119 Sn, and 35 Cl) in these cesium tin(IV) halides has been used to reveal the atomic structure, which plays a key role in the materials’ optical properties. The 119 Sn NMR chemical shifts span approximately 4000 ppm, and the 119 Sn spin-lattice relaxation times span 3 orders of magnitude when the halogen goes from chlorine to iodine in these diamagnetic compounds. Moreover, ultrawideline 35 Cl NMR spectroscopy of Cs 2 SnCl 6 indicates an axially symmetric chlorine electric field gradient tensor with a large quadrupolar coupling constant of ca. 32 MHz, suggesting the presence of a chlorine moiety that is directly attached to Sn(IV) ions. Variable-temperature 119 Sn spin-lattice relaxation time measurements support the presence of dynamics of octahedral SnI 6 units in Cs 2 SnI 6 . We further show that complete mixed-halide solid solutions of Cs 2 SnCl x Br 6– x and Cs 2 SnBr x I 6– x (0 ≤ x ≤ 6) form at any halogen compositional ratio. 119 Sn and 133 Cs NMR spectroscopy resolve the unique local SnCl n Br 6– n and SnBr n I 6– n ( n = 0–6) octahedral and CsBr m I 12– m ( m = 0–12) cuboctahedral environments in the mixed-halide samples. The experimentally observed 119 Sn NMR results are consistent with magnetic shielding parameters obtained by density functional theory computations that were obtained to model the random halogen distribution in mixed-halide analogues. Finally, we demonstrate the difference in the local structures and the optical absorption properties of Cs 2 SnI 6 samples prepared by solvent-assisted and solvent-free synthesis routes.
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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".