Ab Initio Calculations of NMR Parameters for Diatomic Molecules. An Exercise in Computational Chemistry
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Bibliographic record
Abstract
Many scientists seem to be unaware of the relatively simple relationship between nuclear spin-rotation tensors, C, and nuclear magnetic shielding tensors, σ, in linear molecules. The availability of accurate spin-rotation data from high-resolution microwave spectra or molecular beam experiments allows for meaningful comparison between nuclear magnetic shieldings derived from these experimental values and values determined from ab initio calculations, because both results are for "isolated" molecules. Presented here is an undergraduate-graduate-level exercise in the computational quantum chemistry of NMR parameters for a series of fluorine-containing diatomic molecules for which experimental spin-rotation data are available. Calculations carried out at the RHF/6-311++G(2d,2p) level demonstrate the relationship between Ramsey's paramagnetic term, σP, and C. In addition, electric field gradient calculations at this level of theory for Li, Na, K, and Cl in their fluorides qualitatively reproduce experimental trends in the nuclear quadrupolar coupling constants. This exercise will give students an appreciation of the tensorial nature of nuclear magnetic shielding and electric field gradients, an awareness of the relationship between nuclear spin-rotation tensors and nuclear magnetic shielding tensors, insight into the connection between electronic and molecular structure, and hands-on experience in computational chemistry. Implementation of the exercise in a fourth-year undergraduate/first-year graduate course on magnetic resonance was very successful.
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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 | 0.000 | 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 it