Calculations of Electron Transport through Simple π- and σ-Type Radicals
Bibliographic record
Abstract
Organic radicals are of interest in molecular electronics because unpaired electrons lead to degeneracy splitting in other energy levels and such molecules may act as spin filters. This work employs first principles transport calculations using a combination of density-functional theory and a nonequilibrium Green’s function technique to model the electron transport properties of 1,4-benzenediamine (BDA) molecules bridging two Au electrodes. These molecules were substituted in the 2-position with −CH 3, −NH 2, and −OH, and also with their radical analogues −CH 2 •, −NH •, and −O •, which have π-type singly occupied molecular orbitals (SOMO). Spin filter efficiency (SFE) values for these radicals vary as 49%, 27%, and 1% for the −CH 2 •, −NH •, and −O • containing systems, respectively. The large difference is due to the electron affinity of each radical. We found that the radical can indeed accept some charge once it is connected to electrodes, thereby reducing the fraction of excess spin which, in turn, reduces the amount of MO level splitting and the SFE. The transport properties of a radical with a σ-type SOMO were also calculated for a BDA molecule with the H atom in the 2-position of the benzene ring removed. A SFE of 34% was calculated for this system, but most importantly we found that a significant amount of electron transport can indeed occur through a σ-type MO.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| 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".