Energy- versus amplitude-corrected coupled-cluster approaches. III. Accurate computation of spectroscopic data exemplified on the HF molecule
Bibliographic record
Abstract
The so-called energy-corrected coupled-cluster method with singles and doubles (CCSD), which is closely related to the recently proposed method of moments of Kowalski and Piecuch, accounts for the nondynamic correlation effects, which are missing in the standard single-reference CCSD, by projecting onto the modest-size multireference (MR) configuration-interaction SD (CISD) wave function when evaluating the energy, rather than onto the single-determinantal CCSD reference. The ability of this approach to generate reliable potential energy curves (PECs) or surfaces over a wide range of geometries is examined using a realistic ab initio model of the HF molecule. The PECs obtained with the correlation-consistent polarized valence double (triple, quadruple) zeta cc-pVXZ (T,Q) basis sets are used, together with the PEC extrapolated to the complete basis set limit, to compute the rotational and vibrational levels, which are then compared with the experimentally determined values as well as with the directly measured vibrational frequencies. A comparison is also made with the earlier results [X. Li, J. Mol. Struct.: THEOCHEM 547, 69 (2001)] that were obtained with the amplitude-corrected CCSD method, namely the so-called reduced MR CCSD that exploits the same MR CISD wave function, as well as with recently published renormalized CCSD(T) results [P. Piecuch et al., J. Chem. Phys. 115, 5796 (2001)]. It is shown that both the amplitude- and energy-corrected CCSD PECs may be used to generate highly accurate and reliable spectroscopic data once the basis set limit is achieved.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| 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 | 0.000 |
| 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".