Polarizable Force Field with a σ-Hole for Liquid and Aqueous Bromomethane
Bibliographic record
Abstract
Bromomethane (CH3Br) is an acutely toxic environmental pollutant that contributes to ozone depletion. Molecular simulation could be a valuable tool for studying its partitioning and transport in the environment if an accurate molecular model was available. The generalized Amber force field (GAFF), OPLS (optimized potentials for liquid simulations) force field, and CHARMM general force field (CGenFF) were tested for their ability to model the physical properties of liquid bromomethane. The OPLS force field was in fairly good agreement with experiment, while CGenFF and GAFF were significantly in error. The Br Lennard-Jones parameters of the GAFF and CGenFF models were reparameterized, but their radial distribution functions still have significant deviations from those calculated by ab initio molecular dynamics (AIMD). A Drude polarizable force field for bromomethane was parametrized with an off-center positively charged site to represent the C-Br σ-hole. This model is in good agreement with the bulk physical properties and the AIMD RDFs. The modest solubility of bromomethane was reproduced by this model, with dispersion interactions being the dominant water-solute interaction. The water-solute electrostatic interactions are a smaller factor in solubility. This model predicts bromomethane to have a 13 kJ mol(-1) surface excess potential at the water-vapor interface.
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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".