Theoretical investigation of electron transport modulation through benzenedithiol by substituent groups
Notice bibliographique
Résumé
Density functional theory combined with nonequilibrium Green's function techniques was used to model the conduction through disubstituted benzenedithiol molecules bonded to leads composed of 3x3, 5x5 gold and 3x3 aluminum. For the disubstituted 3x3 Au-benzenedithiol-Au systems, the small lead cross section results in a region of nearly zero transmission from -0.4 to -0.2 eV, relative to E(F), due to the absence of lead states. This feature results in negative differential resistance in the current-voltage curves and also causes the main peaks in the transmission spectra, which are dominated by the highest occupied molecular orbitals, to be centered near E(F). The zero-bias transmissions for the disubstituted benzenedithiol, as well as currents at applied biases, correlate very well with the Hammett parameter sigma(p), a quantity that relates the electron donating or withdrawing strength of a substituent. Calculations on disubstituted benzenedithiol connected to 5x5 Au leads produced transmission spectra that showed no gaps over the energy range considered and no negative differential resistance. The transmission in these cases also predominately involves the highest occupied molecular orbitals, and electron donating and withdrawing groups are able to increase and decrease current, respectively. However, there is no strong correlation between current and sigma(p) for this system. This suggests that the correlation observed in the 3x3 Au systems arises from the abrupt cutoff of the main transmission peaks near E(F). The disubstituted 3x3 Al-benzenedithiol-Al systems displayed markedly different behavior from the Au analogs. Electron donating groups and H benzenedithiol-substituted systems display almost no transmission over the energy range considered. However, electron withdrawing group disubstituted benzenedithiol systems had significant peaks in the transmission spectra near E(F), which are associated with the lowest-energy, unoccupied pi-type molecular orbitals. Higher currents are calculated for cases where the substituents have pi-type orbitals that are conjugated with the ring moiety of benzenedithiol. In all cases, the current through the 3x3 Al-benzenedithiol-Al systems is about a factor of 2 less than that through the analogous Au systems. These simulations reveal that the electrical conductance behavior through nanosystems of the type investigated in this work depends on the nature of the molecule as well as the size and composition of the leads to which it is connected. The results suggest that rational design of nanoelectronic systems might be possible under certain conditions but that structure-function relationships cannot be transferred from one system to another.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».