Microsolvation of Alkali and Halide Ions in Acetonitrile Clusters
Bibliographic record
Abstract
The room-temperature thermodynamic and structural properties of acetonitrile clusters containing alkali ions (Na +, Cs + ) or halide ions (I - ) are investigated via Monte Carlo simulations. An intermolecular potential function including Coulombic, polarization, and repulsion−dispersion terms was parameterized on the basis of high-level CCSD(T)/6-311+G(2df,pd)//MP2/6-311+G(d) ab initio calculations, supplemented by experimental data for molecular and ionic polarizabilities. Cluster thermodynamic properties such as binding enthalpies evaluated from the Monte Carlo simulations are in good agreement with available experimental data, which inspires confidence in the simulation results. These properties are shown to converge very slowly to their bulk limit, in agreement with earlier predictions of the liquid drop model, and their evolution with cluster size is closely related to the solvation structure of the ionic clusters. All Na + (CH 3 CN) n, Cs + (CH 3 CN) n, and I - (CH 3 CN) n clusters exhibit an interior solvation structure. However, if the Na + (CH 3 CN) n and Cs + (CH 3 CN) n room-temperature radial probability distributions exhibit very distinct, sharp peaks, those for large I - (CH 3 CN) n clusters are broader, because of much weaker iodide−solvent interactions. The solvent coordination numbers for the first solvation shell are ca. 6, 7, and 9 for Na + (CH 3 CN) n, Cs + (CH 3 CN) n and I - (CH 3 CN) n clusters, respectively. The completion of the ion first solvation shell is accompanied by a significant decrease of the stepwise binding enthalpies, a finding that is more pronounced for cationic clusters. Finally, comparison with previous results for ion−water clusters demonstrated the importance of the relative strengths of ion−solvent and solvent−solvent interactions in the determination of interior vs surface ionic cluster structures. For example, I - (CH 3 CN) n clusters clearly exhibit an interior solvation structure, in net contrast with the surface structures observed for I - (H 2 O) n clusters.
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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 | 0.001 | 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".