Thermal Expansion Behavior of M<sup>I</sup>[AuX<sub>2</sub>(CN)<sub>2</sub>]-Based Coordination Polymers (M = Ag, Cu; X = CN, Cl, Br)
Bibliographic record
Abstract
Two sets of trans- [AuX 2 (CN) 2 ] − -based coordination polymer materials—M[AuX 2 (CN) 2 ] (M = Ag; X = Cl, Br or M = Cu; X = Br) and M[Au(CN) 4 ] (M = Ag, Cu)—were synthesized and structurally characterized and their dielectric constants and thermal expansion behavior explored. The M[AuX 2 (CN) 2 ] series crystallized in a tightly packed, mineral-like structure featuring 1-D trans- [AuX 2 (CN) 2 ] − -bridged chains interconnected via a series of intermolecular Au···X and M···X (M = Ag, Cu) interactions. The M[Au(CN) 4 ] series adopted a 2-fold interpenetrated 3-D cyano-bound framework lacking any weak intermolecular interactions. Despite the tight packing and the presence of intermolecular interactions, these materials exhibited decreased thermal stability over unbound trans- [AuX 2 (CN) 2 ] − in [ n Bu 4 N][AuX 2 (CN) 2 ]. A significant dielectric constant of up to ε r = 36 for Ag[AuCl 2 (CN) 2 ] (1 kHz) and a lower ε r = 9.6 (1 kHz) for Ag[Au(CN) 4 ] were measured and interpreted in terms of their structures and composition. A systematic analysis of the thermal expansion properties of the M[AuX 2 (CN) 2 ] series revealed a negative thermal expansion (NTE) component along the cyano-bridged chains with a thermal expansion coefficient (α CN ) of −13.7(11), −14.3(5), and −11.36(18) ppm·K –1 for Ag[AuCl 2 (CN) 2 ], Ag[AuBr 2 (CN) 2 ], and Cu[AuBr 2 (CN) 2 ], respectively. The Au···X and Ag···X interactions affect the thermal expansion similarly to metallophilic Au···Au interactions in M[Au(CN) 2 ] and AuCN; replacing X = Cl with the larger Br atoms has a less significant effect. A similar analysis for the M[Au(CN) 4 ] series (where the volume thermal expansion coefficient, α V, is 41(3) and 68.7(19) ppm·K –1 for M = Ag, Cu, respectively) underscored the significance of the effect of the atomic radius on the flexibility of the framework and, thus, the thermal expansion properties.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".