Improving “difficult” reaction barriers with self-interaction corrected density functional theory
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Bibliographic record
Abstract
We examined 11 difficult reactions with self-interaction corrected density (SIC) functional theory. The data set includes dissociation of radicals into symmetric fragments (H2+→H+H+, He2+→He+He+), radical hydrogen abstraction (H+H2→H2+H, H+HCl→H2+Cl, H+N2H2→N2H+H2, CH3+H2→CH4+H), proton transfer [HC(OH)CHC(O)H→HC(O)CHC(OH)H], SN2 halogen exchange (X−+CH3X→CH3X+X−, X=F,Cl,Br), and closed-shell unimolecular dissociation of tetrasine (C2N4H2→N2+2HCN). Calculated self-interaction energies cancel, almost identically, for the reaction energies (ΔER), so that SIC functionals do not lead to a systematic improvement in ΔER. Self-interaction correction increases for reaction transition structures, leading to higher calculated activation barriers (ΔE≠). The average absolute deviation in ΔE≠, from ab initio and experimental barriers, is reduced from 14 kcal/mol for Vosko–Wilk–Nusair (VWN) or 12 kcal/mol for revised Perdew–Burke–Ernzerhof (revPBE) functionals to 5.4 (SIC-VWN) or 3.4 (SIC-revPBE) kcal/mol. Reorganization of the electron density, due to removal of self-interaction, appears to be important. When SIC is included as a perturbation, using self-consistent densities of the parent functional, the average absolute deviations for the barriers increase to 7.5 (VWN+SIC) or 5.3 (revPBE+SIC) kcal/mol. Gradient-corrected functionals (revPBE, BP86) reduce the magnitude of the total self-interaction correction, by improving the description of the core orbitals. For the valence orbitals, both the magnitudes of the self-interaction corrections, and their change between reagents and transition structures, are similar for VWN local density approximation, and generalized gradient approximation functionals. Reducing the magnitude of the self-interaction energy for valence electrons thus appears to be a promising direction for the development of chemically accurate exchange-correlation functionals.
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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 | 0.001 |
| 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 it