Uncovering Halogen Mixing and Octahedral Dynamics in Cs <sub>2</sub> SnX <sub>6</sub> by Multinuclear Magnetic Resonance Spectroscopy
Bibliographic record
Abstract
Cs2SnX6 (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 (133Cs, 119Sn, and 35Cl) 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 119Sn NMR chemical shifts span approximately 4000 ppm, and the 119Sn spin-lattice relaxation times span 3 orders of magnitude when the halogen goes from chlorine to iodine in these diamagnetic compounds. Moreover, ultrawideline 35Cl NMR spectroscopy of Cs2SnCl6 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 119Sn spin-lattice relaxation time measurements support the presence of dynamics of octahedral SnI6 units in Cs2SnI6. We further show that complete mixed-halide solid solutions of Cs2SnClxBr6–x and Cs2SnBrxI6–x (0 ≤ x ≤ 6) form at any halogen compositional ratio. 119Sn and 133Cs NMR spectroscopy resolve the unique local SnClnBr6–n and SnBrnI6–n (n = 0–6) octahedral and CsBrmI12–m (m = 0–12) cuboctahedral environments in the mixed-halide samples. The experimentally observed 119Sn 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 Cs2SnI6 samples prepared by solvent-assisted and solvent-free synthesis routes.
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How this classification was reachedexpand
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 | 0.000 | 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) | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".