Energetics of naphthynes — Performance of reduced multi-reference coupled-cluster methods for diradicals
Bibliographic record
Abstract
The energetics of all the possible isomers of the didehydronaphthalene (naphthalyne or naphthyne) diradical has been examined using the reduced multi-reference (RMR) coupled-cluster (CC) method with singles and doubles (RMR CCSD) that employs a modest size MR CISD wave function as an external source of the most important (primary) triples and quadruples to account for nondynamic correlation effects in the presence of quasi-degeneracy, as well as by its perturbatively corrected version for the secondary triples, the RMR CCSD(T) method. The resulting energies are compared with those obtained by the standard single-reference (SR) CCSD and CCSD(T) approaches. In all cases, we used both the cc-pVDZ basis set, as well as its restricted version cc-pVDZ* with deleted p-functions on hydrogens. Once the optimal geometry for each isomer was found, we computed the energy of the lowest-lying singlet and triplet states using the above mentioned CC methods, as well as the implied singlet–triplet splittings. These results enabled us to classify the isomers into three groups according to their stability and to determine, whenever possible, the spin multiplicity of the ground state. Finally, we point out the relationship between the extent of the diradical character of naphthyne isomers, the degree of their MR nature, the distance separating the radical centers, and, finally, the size of the largest doubly-excited cluster amplitude in their CC wave functions.
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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 | 0.001 | 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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".