Theoretical study on the core-excited states of the allyl using multi-reference methods with core–valence separation (CVS) approximation
Bibliographic record
Abstract
The multi-state n-electron valence second-order perturbation theory with core-valance separation (CVS) approximation (CVS-MS-NEVPT2) and static-dynamic-static multi-state multi-reference second-order perturbation theory with CVS (CVS-SDSPT2) were developed based on the internally contracted multi-reference configuration interaction method with single and double excitations with CVS (CVS-icMRCISD) [Song et al., J. Chem. Phys. 160, 094114 (2024)] due to their high similarity and inheritance in theoretical frameworks and computational implementation. Benchmark calculations demonstrate that these perturbation methods significantly improved computational efficiency while maintaining comparable accuracy to the CVS-icMRCISD method. Moreover, the core-excited states of the allyl system were used as a pilot application for three CVS-multi-reference methods. The CVS-icMRCISD method produced four excited states at 282.10, 285.11, 286.18, and 288.07 eV, accurately reproducing four distinctive peaks (A, B, C, and D) in the experimental x-ray absorption spectra (XAS). Theoretical excitation energies of two core-excited states of the allyl cation (282.64 and 286.88 eV) align with the peaks observed at 282.52 and 286.92 eV in the experimental XAS. However, vibrational analysis of the X-A transition suggests that the α band in the experimental XAS might arise from electronic-vibronic coupling between the antisymmetric stretching of C-H bonds in the -CTH2 group and the core-excited state, leaving the assignment of the α band ambiguous. Overall, the CVS-icMRCISD method achieved excellent agreement with experimental results, with an average deviation of 0.25 eV. While the errors of CVS-SDSPT2 and CVS-MS-NEVPT2 methods were slightly larger, both methods maintained acceptable accuracy, making them suitable for medium-sized molecules by significantly reducing computational costs.
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 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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".