Relativistic Effects for NMR Shielding Constants in Transition Metal Oxides Using the Zeroth-Order Regular Approximation
Bibliographic record
Abstract
Relativistic effects for NMR shielding constants have been calculated using the zero order regular approximation (ZORA) for relativistic effects. Isotropic NMR shielding constants were obtained using density functional theory with gauge including atomic orbitals (GIAO) in a spin-free formalism for the metal nuclei in transition metal oxides MO 4 n - (M = Cr, Mn, Fe, Mo, Tc, Ru, W, Re, Os) and carbonyl complexes M(CO) 6 (M = Cr, Mo, W). The ZORA isotropic shieldings are compared with results from an extended version of the relativistic method employing the Pauli Hamiltonian developed earlier by Schreckenbach and Ziegler. Comparison between ZORA and Pauli shieldings, employing the restrictions necessary for the Pauli approach frozen cores, restricted basis sets in the core region show the ZORA shieldings to be significantly different from Pauli ones, but the chemical shifts of the metal oxides with respect to the carbonyl complexes do not differ much. However, extending the ZORA calculations (no frozen core, extended basis sets) gives significant changes, proving the limitation to frozen cores and restricted basis sets of the Pauli method to be unwarranted. Comparison to experiment shows that the errors of the most precise ZORA chemical shifts are ca. 10% (in the order of a few 100 ppm) for both the light and heavy transition metals. Error sources may be, apart from deficiencies of the density functional, the neglect of spin−orbit coupling and the neglect of solvent effects.
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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 | 0.002 | 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".