Investigating colossal thermal expansion driven by chalcogen bonds using AB(XCN)<sub>4</sub> (A = Co, Zn, Cd; B = Cd, Hg; X = S, Se) compounds
Bibliographic record
Abstract
The thermal expansion of eight compounds from the well-known AB(XCN) 4 family of thiocyanate- and selenocyanate-bridged frameworks (A = Co, Zn, Cd; B = Cd, Hg; X = S, Se) has been studied using single-crystal X-ray crystallography and Raman spectroscopy, to investigate the influence of chalcogen bonding interactions. In the case of ZnHg(SCN) 4 , biaxial negative thermal expansion (−6.9(9) ppm K −1 ) along the a and b axes was observed, occurring elastically due to the colossal positive thermal expansion (124.3(18) ppm K −1 ) along the c axis driven by weak S···S interactions. Substituting the thiocyanate groups with selenocyanate groups, i.e., with ZnHg(SeCN) 4 , caused a decrease in the anisotropic behaviour, due to stronger Se···Se interactions suppressing the expansion (α a = −0.4(15) ppm K −1 ; α c = 90.0(17) ppm K −1 ). Replacing Zn with Cd was found to also suppress the anisotropic behaviour—regardless of the chalcogen used—while placing Cd at the B site enhanced the anisotropic behaviour. The effect of replacing Zn with Co was less clear, likely due to their similar size. Overall, the results illustrate how weak chalcogen bonds can drive colossal thermal expansion, leading to biaxial negative or zero thermal expansion.
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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 | 0.001 | 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 | 0.001 |
| 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 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".