Reorganization free energies and quantum corrections for a model electron self-exchange reaction: comparison of polarizable and non-polarizable solvent models
Bibliographic record
Abstract
The solvent contribution to the reorganization free energy for electron self-exchange in aqueous Ru(II)–Ru(III) is computed for two recently developed polarizable water models, AMOEBA [J. Phys. Chem. B 107, 5933 (2003)] and SWM4-NDP [Chem. Phys. Lett. 418, 241 (2005)], and for the earlier POL3 model [J. Phys. Chem. 99, 6208 (1995)], and compared with the reorganization free energy of non-polarizable water models. The ‘solute’, defined as the two ions and their first hydration shells, is treated as non-polarizable. We find that the solvent (‘outer sphere’) reorganization free energy is reduced by 22% for SWM4-NDP and by 11% for POL3 relative to the non-polarizable TIP3P water, but increased by 5% for AMOEBA water. This is less than the ≈38% reduction suggested by standard continuum theory and confirms the view that continuum theory predicts a stronger dependence of solvent reorganization on the optical dielectric constant than what is obtained from atomistic simulation. The varying degree of reduction in reorganization free energy for polarizable water models is the consequence of two opposing effects: (i) reduction in reorganization free energy due to decreased electronic response; and (ii) increase in reorganization free energy due to increased nuclear response. The first effect gives a consistent decrease of about 30%, while the second effect strongly depends on the polarizable water model used and is largest for AMOEBA water. Rate enhancements due to quantum corrections are computed in the harmonic bath approximation and range between 3.8 and 10.9, in good agreement with the estimate obtained from experimental dispersion data of liquid water, 7.7. The rigid non-polarizable water models overestimate the quantum correction in the libration modes, which effectively compensates for the neglect of quantum corrections in the absent stretching modes. About 85% of the solvent reorganization is due to the second and third solvation shell of the ion pair. Size effects caused by the finite number of solvent molecules are minor and much smaller than for oxidation of a single ion.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".