| 1. |
- Chen, Lan, et al.
(författare)
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Mechanism for negative differential resistance in molecular electronic devices : Local orbital symmetry matching
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:14
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Tidskriftsartikel (refereegranskat)abstract
- A new mechanism for negative differential resistance (NDR) originating from local orbital symmetry matching between an electrode and a molecule in a single molecular electronic device is proposed and demonstrated by a joint experimental and theoretical scanning tunneling microscope study of a cobalt phthalocyanines (CoPc) molecule on a gold substrate. For two different metal tips used, Ni and W, NDR occurs only with Ni tips and shows no dependence on the geometrical shape of the tip. Calculations reveal that such a behavior is a result of local orbital symmetry matching between the Ni tip and Co atom.
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| 2. |
- Fu, Qiang, et al.
(författare)
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First-principles calculations of adsorption and dehydrogenation of trans-2-butene molecule on Pd(110) surface
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:15
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption and dehydrogenation processes of trans-2-butene molecule on the Pd(110) surface have been studied by density functional theory calculations. Different adsorption configurations of the reactant, the dehydrogenated product, and the most favorable reaction pathway have been determined. The calculated energy barrier agrees well with the value deduced from experiments. It is found that the reactant molecule must undergo a rotation before the C-H bond cleavage, and surface Pd atoms are involved in the dehydrogenation reaction through the formation of the Pd-C-H three-membered metallacycle. Our calculations have not only provided reliable interpretation for various experimental observations but also shed more light on the dynamics of the reaction processes.
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| 3. |
- Fu, Qiang, et al.
(författare)
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Mechanism for tautomerization induced conductance switching of naphthalocyanin molecule
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:18
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Tidskriftsartikel (refereegranskat)abstract
- Reaction mechanism for tautomerization process of a single naphthalocyanin molecule has been studied using density functional theory. It is found that tautomerization of the naphthalocyanin molecule is not a concerted reaction, but a step-wise process in that one hydrogen atom transfers after another. A stable intermediate state and the possible transition state of the reaction processes have been located. The occurrence of the intermediate state suggests that the tautomerization induced conductance switching involves four conductance states with different conductances, and the earlier proposed two-state system model is not valid.
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| 4. |
- Hao, Ren, et al.
(författare)
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Simulation of inelastic electronic tunneling spectra of adsorbates from first principles
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:134707
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Tidskriftsartikel (refereegranskat)abstract
- We present first-principles simulations for inelastic electron tunneling spectra of molecules adsorbed on metal surface as measured in scanning tunneling microscopy experiments. Both elastic and inelastic tunneling processes are modeled in terms of Tersoff-Hamann approximation with a full vibration analysis at density functional theory levels. The calculated spectra of carbon oxide and acetylene molecules adsorbed on Cu(100) surface have well reproduced their experimental counterparts. The inelastic electron tunneling images of the observable vibration modes have been provided. The performance of gradient-corrected density functional is compared with that of local density functional.
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| 5. |
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| 6. |
- Li, Zhenyu, et al.
(författare)
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How Graphene is Cut upon Oxidation?
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:18, s. 6320-6321
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Tidskriftsartikel (refereegranskat)abstract
- Our first principles calculations reveal that an oxidative cut of graphene is realized by forming epoxy and then carbonyl pairs. Direct formation of a carbonyl pair to tear graphene up from an edge position is not favorable in energy. This atomic picture is valuable for developing effective means of graphene manipulation. The proposed epoxy pairs may be related to some long puzzling experimental observations on graphene oxide.
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| 7. |
- Monti, Susanna, et al.
(författare)
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Effects due to interadsorbate interactions on the dipeptide/TiO2 surface binding mechanism investigated by molecular dynamics simulations
- 2007
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:21, s. 7765-7771
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Tidskriftsartikel (refereegranskat)abstract
- Classical molecular dynamics simulations, supported by ab initio periodic calculations, were carried out to investigate peptide adsorption mechanisms onto a rutile (110) TiO2 layer in the presence of water molecules. Different binding modes, comprising multiple coordination to the titanium atoms, of several conformers, simultaneously adsorbed upon the surface, were analyzed in detail. In agreement with experimental and theoretical findings, peptide carbonyl oxygens and nitrogens were found to be possible coordination atoms. Local effects were responsible of adsorption and desorption events and intermolecular interactions induced conformational changes and reorientations of the molecules with respect to the surface that produced both strongly and weakly adsorbed species.
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| 8. |
- Pan, Shuan, et al.
(författare)
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Design and control of electron transport properties of single molecules
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:36, s. 15259-15263
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate in this joint experimental and theoretical study how one can alter electron transport behavior of a single melamine molecule adsorbed on a Cu (100) surface by performing a sequence of elegantly devised and well-controlled single molecular chemical processes. It is found that with a dehydrogenation reaction, the melamine molecule becomes firmly bonded onto the Cu surface and acts as a normal conductor controlled by elastic electron tunneling. A current-induced hydrogen tautomerization process results in an asymmetric melamine tautomer, which in turn leads to a significant rectifying effect. Furthermore, by switching on inelastic multielectron scattering processes, mechanical oscillations of an N-H bond between two configurations of the asymmetric tautomer can be triggered with tuneable frequency. Collectively, this designed molecule exhibits rectifying and switching functions simultaneously over a wide range of external voltage.
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| 9. |
- Zhang, Wenhua, et al.
(författare)
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Electronic structure of [121]tetramantane-6-thiol on gold and silver surfaces
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:054705
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism for electron photoemission of [121]tetramantane and its functionalized compound [121]tetramantane-6-thiol adsorbed on different noble metal surfaces has been investigated by density functional theory calculations. It is found that good chemical bonding between molecules and metal surfaces is a helpful but not a necessary condition for electron photoemission. A lower work function and weaker hybridization between the molecule and the metal could lead to much more efficient electron photoemission. It is observed that, neglecting final state effect, a simple ground state picture cannot result in negative electron affinity for the systems under investigation. Calculations have shown that by exciting an electron in the lowest unoccupied molecular orbital, the highest singly occupied molecular orbital of the molecule can be shifted above the vacuum level, resulting in negative electron affinity and emission of the accumulated electrons.
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| 10. |
- Zhang, Wenhua, et al.
(författare)
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First Principles Study on the Geometric and Electronic Structures of the FeO/Pt(111) Surface
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:19, s. 8302-8305
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Tidskriftsartikel (refereegranskat)abstract
- The geometric, electronic, and magnetic properties of the FeO monolayer on a Pt(111) surface are investigated by first principles calculations. Generally, antiferromagnetic (AFM) structures are more stable than that of the ferromagnetic one. On the basis of a specific AFM structure, the long puzzling scanning tunneling microscopy (STM) experimental observations can be well explained. In this AFM model, the Fe-O layer distance at the fee region is larger than the hcp region, in contrast to previous theoretical results. The STM images at the field-emission regime are explained by local surface potential.
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