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  • 1. Leng, Jian-Cai
    et al.
    Lin, Li-Li
    Song, Xiu-Neng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Li, Zong-Liang
    Wang, Chuan-Kui
    Orientation of Decanethiol Molecules in Self-Assembled Monolayers Determined by Inelastic Electron Tunneling Spectroscopy2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 42, p. 18353-18357Article in journal (Refereed)
    Abstract [en]

    We present first-principles calculations for the inelastic electron tunneling spectroscopy (IETS) of decanethiolate molecules sandwiched between Au(111) surface and scanning tunneling microscope (STM) reported by Hallback et at, (Nano Left. 2004, 4, 2393). It is demonstrated here that the IET spectra are very sensitive to the molecule-metal contact structure, orientation of the molecule adsorbed on the surface, and the distance between the carbon of the terminal methyl group and the STM tip. With correct assignation of the experimental spectral features, the orientation of the molecule and then the probable configuration of the molecular junction are

  • 2. Lin, Li-Li
    et al.
    Leng, Jian-Cai
    Song, Xiu-Neng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Li, Zong-Liang
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wang, Chuan-Kui
    Effect of Aromatic Coupling on Electronic Transport in Bimolecular Junctions2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 32, p. 14474-14477Article in journal (Refereed)
    Abstract [en]

    We have performed a systematic first-principles study on conductance-voltage characteristics of bioligo(phenylene ethynylene)-monothiol molecular junctions as recently reported by Wu et al.[Nalure Nanotech. 2008, 3, 569]. It is found that the molecular conductance is very sensitive to the vertical distance between two molecules as well as the titled angle between two molecular planes. By comparing with experimental results, key structure parameters for bimolecular junction are determined, indicating that in the experimental devices, the vertical distance between two molecules is around 0.30 mn, the two planar molecules have a cofacial arrangement, and the length of the molecular bridge is about 2.88 nm. The underlying mechanism for electron transport in these aromatically coupled bimolecular junctions has also been discussed.

  • 3.
    Lin, Li-Li
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Song, Xiu-Neng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Leng, Jian-Cai
    Li, Zong-Liang
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wang, Chuan-Kui
    Determination of the Configuration of a Single Molecule Junction by Inelastic Electron Tunneling Spectroscopy2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 11, p. 5199-5202Article in journal (Refereed)
    Abstract [en]

    First-principles calculations for inelastic electron tunneling spectroscopy (IETS) of a single 1,3-propanedithiol molecule covalently bound to gold electrodes are presented. Inelastic electron tunneling spectra of the single molecule junction with different contact geometries and molecular orientations at the interface are simulated. It is demonstrated that the delicate variation in the configuration of the single molecule junction caused by separating the two electrodes call result in significant changes in the inelastic electron tunneling spectral profile of the junction. The two Most probable configurations of the molecular junction formed in the experiment (Nano Lett. 2008, 8, 1673) are theoretically identified, and the experimental IET spectra are correctly assigned.

  • 4.
    Lin, Li-Li
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Song, Xiu-Neng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wang, Chuan-Kui
    Formation and electronic transport properties of bimolecular junctions based on aromatic coupling2010In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 22, no 32, p. 325102-Article in journal (Refereed)
    Abstract [en]

    A systematic first-principles study on conductance-voltage characteristics of bi-(quasi) oligo(phenylene ethynylene)-monothiol molecular junctions reported by Wu et al (2008 Nat. Nanotechnol. 3 569) is presented. The so-called ortho-and para-conformations of the bimolecular junction are considered. Our calculation indicates that the bimolecular junction prefers to take the ortho-conformation because of its lower energy. The simulation supports the experimental findings that aromatic coupling between two molecules is strong enough to induce the formation of molecular junctions. By comparing with experimental results, structure parameters for a probable bimolecular junction are determined. The underlying mechanism for formation of the bimolecular junction and its electron transport is discussed.

  • 5.
    Ma, Yong
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ai, Yuejie
    North China Electric Power University, Beijing, China.
    Song, Xiuneng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Chuankui
    Shandong Normal University.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    The equilibrium geometry of A@C60: A test case for conventional density functional theory2014In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 591, p. 312-316Article in journal (Refereed)
    Abstract [en]

    Potential energy surfaces (PESs) along the reaction pathway towards the center of CC bond between two six membered rings for ten different endohedral fullerenes A@C60 (A = H, C, O, S, N, P, He, Ne, Ar, Kr) have been studied by density functional theory (DFT) and Hartree-Fock (HF) method. The results show that no suitable method can consistently describe the interaction between atom A and carbon cage. The dispersion corrected DFT methods fail to describe the equilibrium geometry and PES of the complexes with light atoms. Nevertheless, the inclusion of the dispersion stabilizes the system as reflected by interaction energies (IEs) between atom A and C60.

  • 6.
    Song, Xiuneng
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Theoretical Characterization of Functional Molecular Materials2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nowadays, material, energy and information technologies are three pillar industries. The materials that have close relation with our life have also been the foundation for the development of energy and information technologies. As the new member of the material family, functional molecular materials have become increasingly important for many applications, for which the design and characterization by the theoretical modeling have played the vital role. In this thesis, three different categories of functional molecular materials, the endohedral fullerenes, the fullerene derivatives and the self-assembled monolayers (SAMs), have been studied by means of first principles methods.

    The non-metal endohedral fullerene N@C60 is a special endohedral fullerene that is believed to be relevant to the construction of future quantum computer. The energy landscape inside the N@C60 has been carefully explored by density functional theory (DFT) calculations. The most energy favorable potential energysurfaces (PESs) for the N atom to move within the cavity have been identified. The effect of the charging on the PESs has also been examined. It is found that the inclusion of dispersion force is essential in determining the equilibriumstructure of N@C60. Furthermore, the performance of several commonly useddensity functionals with or without dispersion correction has been verified for ten different endohedral fullerenes A@C60 with the atom A being either reactive nonmetal or nobel gases elements. It shows that the inclusion of the dispersion forcedoes provide better description for the binding energy (BE), however, none ofthem could correctly describe the energy landscape inside all the ten endohedral fullerenes exclusively. It thus calls for the further improvement of current density functionals for weak interacting systems.

    Soft X-ray spectroscopy is a powerful tool for studying the chemical and electronic structures of functional molecular materials. Theoretical calculations have been proven to be extremely useful for providing correct assignments for spectraof large systems. In this thesis, we have performed first principles simulations forthe near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectra (XPS) of fullerene derivatives and aminothiolates SAMs. Our calculatedspectra can accurately reproduce experimental results available for all the systemsunder investigations, and identify the species or structures that are responsible for those unexpected spectral features observed in experiments. We have suggested a modified building block (MBB) approach that allows to calculate NEXAFS spectraof a large number of fullerene derivatives with very small computational cost, and resolved the long standing puzzle around the experimental XPS and NEXAFS spectra of SAMs with aminothiolates.

  • 7.
    Song, Xiuneng
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, Weijie
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ma, Yong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Chuankui
    Shandong Normal University.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Theoretical study of core excitation spectroscopy of fullerene-based solarcell acceptorsArticle in journal (Other academic)
  • 8.
    Song, Xiuneng
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hua, Weijie
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ma, Yong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Chuankui
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Theoretical Study of Core Excitations of Fullerene-Based Polymer Solar Cell Acceptors2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 45, p. 23938-23944Article in journal (Refereed)
    Abstract [en]

    First-principles simulations for the C K-edge X-ray photoelectron (XPS) and near-edge X-ray fine-structure (NEXAFS) spectra of representative polymer solar cell acceptor (PSCA) molecules have been carried out with special focuses on the [6,6]-phenyl-Cn+1-butyric acid methyl ester (PCnBM, n = 60, 70, 84). In the XPS spectra, evident red shift of core binding energies are observed in PCnBM as compared to the corresponding fullerene C-n, which is due to weak electronic charge transfer from the side chain to the fullerene backbone and consequently increased electron screening. Special emphasis is paid to a spectral peak at ca. 284.7 eV, which is caused by resonances of phenyl-ring carbons in the side chain and is important in characterizing the electronic structures of different PSCA molecules. Additionally, we propose a modified version of the building block (MBB) approach for quick estimation of the NEXAFS spectra, which is useful when computational resources are limited or massive systems are under study. This method is based on our component analysis on the side chain and fullerene backbone parts and adds only a further empirical fine-tuning after the conventional BB approach. Our calculated results are in good agreement with available experiments.

  • 9.
    Song, Xiuneng
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ma, Yong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Chuankui
    Shandong Normal University, Shandong, Peoples R China.
    Dietrich, Paul M.
    BAM Fed Inst Mat Res & Testing, Berlin, Germany .
    Unger, Wolfgang E. S.
    BAM Fed Inst Mat Res & Testing, Berlin, Germany .
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Effects of Protonation, Hydrogen Bonding, and Photodamaging on X-ray Spectroscopy of the Amine Terminal Group in Aminothiolate Monolayers2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 23, p. 12649-12654Article in journal (Refereed)
    Abstract [en]

    The amine head group, NH2, in aminothiolate monolayers can often generate unexpectedly rich structures in its N K-edge X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra that are difficult to assign. We have carried out density functional theory (DFT) calculations to study the XPS and NEXAFS of amine head group in four different aminothiolate monolayers, namely aliphatic 11-aminoundecane-1-thiol (AUDT), aromatic 4-aminobenzenethiol (ABT) and araliphatic 4-aminophenylbutane-1-thiol (APBT) and 3-(4”-amino-1,1’:4’,1”-terphenyl-4-yl)propane-1-thiol (ATPT), with the focus on structure changes caused by protonation, hydrogen bonding and X-ray damaging. Spectra of all possible saturated and unsaturated species, as well as X-ray damage products, such as imine, nitrile, azo species and cumulative double bonds, have been thoroughly examined. It is found that extra spectral structures observed in the experimental XPS spectra are not resulted from protonation, but from the formation of a primary ammonium. The X-ray excitation can induce cross linking between two neighboring molecules to form different complexes that contribute to the π features in NEXAFS spectra.

  • 10.
    Song, Xiuneng
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yong, Ma
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Chuankui
    Shandong Normal University.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Energy landscape inside the cage of neutral and charged N@C602011In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 517, no 4-6, p. 199-203Article in journal (Refereed)
    Abstract [en]

    Potential energy surfaces along different escaping paths of the nitrogen atom inside the neutral and charged endohedral fullerene N@C60 have been constructed at the density functional theory level. It is found that the dispersion force plays an important role in determining the equilibrium geometry of the neutral system. The most energetic favorable escaping path is towards the center of C = C/C–C bond connecting two neighboring rings for all three systems. The rate determining potential energy surface shows a very small dependence on the charging state. The presented theoretical results should be useful for the practical applications of N@C60 in quantum computing and information.

1 - 10 of 10
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