Externally Corrected Coupled-Cluster Approaches: Energy versus Amplitude Corrected CCSD
Bibliographic record
Abstract
The externally corrected coupled-cluster methods with singles and doubles (ecCCSD), which exploit some independently available wave function as a source of higher-than-pair clusters, are considered. The focus is on methods that employ a modest-size multireference (MR) configuration interaction (with singles and doubles, CISD) wave function as the external source. Both the amplitude- and energy-corrected CCSD methods are employed, the former correcting the standard single reference (SR) CCSD equations for triples and quadruples, while the latter accounts for the nondynamic correlation effects when evaluating the energy by employing the MR CISD wave function in lieu of the single determinantal (usually Hartree-Fock) reference in the asymmetric energy formula. The performance and relationship of both types of approaches is illustrated by computing the rotational and vibrational energy levels using the potential generated by these various methods and by comparing the calculated spectra with the experimental ones for the simplest first-row hydride, namely the LiH molecule. A special attention is paid to the role of core-correlation effects, in which case we also consider the HF molecule.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 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".