PKVe9'Rrefs.MYD}?FSaraiva-Souza, A. Sumpter, B. G. Meunier, V. Souza, A. G. Del Nero, J.2008/Electrical rectification in betaine derivatives 12008-12011Journal of Physical Chemistry C11231AugWe theoretically investigate the electric rectification in an organic two terminal push-pull molecular device using a combination of ab initio techniques. Our main finding is that the electric rectification is extremely sensitive to the length of the chain, undergoing a complete switching after a specific chain length. This unique process occurs for betaine-like donor-g bridge-acceptor systems and is directly associated with a conjugated bridge in the presence of an external electric field. The conjugated bridge between the donor and acceptor groups is composed of oligoethylene with sizes ranging from 0 to 10 C=C units. The appearance of electric rectification occurs when the bridge size is equal to 5 units and is complete for those larger than 6 units (i.e., full inversion). This new electronic effect is advantageous for the design of large hybrid organic/inorganic circuits with an increased majority carrier flow that is necessary for the emerging needs of nanotechnology.://000258147200057 1932-7447ISI:00025814720005710.1021/jp801667q }?'Huang, J. S. Sumpter, B. G. Meunier, V.2008~A universal model for nanoporous carbon supercapacitors applicable to diverse pore regimes, carbon materials, and electrolytes 6614-6626Chemistry-a European Journal1422X Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model, which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopofe regime (2-50 nm), counterions enter mesoporous carbon materials and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (<2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (>50 nm) at which pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, which show the significant effects of pore curvature on the supercapacitor properties of nanoporous carbon materials. It is shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials, including activated carbon materials, template carbon materials, and novel carbide-derived carbon materials, and with diverse electrolytes, including organic electrolytes, such as tetraethylammonium tetrafluoroborate (TEABF(4)) and tetraethylammonium methylsulfonate (TEAMS) in acetonitrile, aqueous H2SO4 and KOH electrolytes, and even an ionic liquid electrolyte, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size It may lend support for the systematic optimization of the properties of carbon supercapacitors through experiments. On the basis of the insight obtained from the new model, we also discuss the effects of the kinetic solvation/desolvation process, multimodal (versus unimodal) pore size distribution, and exohedral (versus endohedral) capacitors on the electrochemical properties of supercapacitors.://000258217000008 0947-6539ISI:00025821700000810.1002/chem.200800639vx}?9Romo-Herrera, J. M. Terrones, M. Terrones, H. Meunier, V.2008HElectron transport properties of ordered networks using carbon nanotubes315704Nanotechnology1931AugThe electronic transport properties of ordered networks using carbon nanotubes as building blocks (ON-CNTs) are investigated within the framework of a multiterminal Landauer -Buttiker formalism using an s, p(x), p(y), p(z) parameterization of the tight-binding Hamiltonian for carbon. The networks exhibit electron pathway selectiveness, which is shown to depend on the atomic structure of the network nodes imposed by the specific architecture of the network and the distribution of its defects (non-hexagonal rings). This work represents the first undersF}?%Beste, A. Meunier, V. Harrison, R. J.2008Electron transport in open systems from finite-size calculations: Examination of the principal layer method applied to linear gold chainsJournal of Chemical Physics12815Apr|We describe the occurrence of computational artifacts when the principal layer method is used in combination with the cluster approximation for the calculation of electronic transport properties of nanostructures. For a one-dimensional gold chain, we observe an unphysical band in the band structure. The artificial band persists for large principal layers and for large buffer sizes. We demonstrate that the assumption of equality between Hamiltonian elements of neighboring layers is no longer valid and that a discontinuity is introduced in the potential at the layer transition. The effect depends on the basis set. When periodic boundary conditions are imposed and the k-space sampling is converged, the discontinuity disappears and the principal layer method can be correctly applied by using a linear combination of atomic orbitals as basis set. (c) 2008 American Institute of Physics.://000255228900083 0021-9606ISI:000255228900083154713 10.1063/1.2905219{}?rRomo-Herrera, J. M. Sumpter, B. G. Cullen, D. A. Terrones, H. Cruz-Silva, E. Smith, D. J. Meunier, V. Terrones, M.2008UAn atomistic branching mechanism for carbon nanotubes: Sulfur as the triggering agent 2948-2953'Angewandte Chemie-International Edition4716://000254934200006 1433-7851ISI:00025493420000610.1002/anie.200705053}?Cruz-Silva, E. Cullen, D. A. Gu, L. Romo-Herrera, J. M. Munoz-Sandoval, E. Lopez-Urias, F. Sumpter, B. G. Meunier, V. Charlier, J. C. Smith, D. J. Terrones, H. Terrones, M.2008xHeterodoped nanotubes: Theory, synthesis, and characterization of phosphorus-nitrogen doped multiwalled carbon nanotubes441-448Acs Nano23Mar6Arrays of multiwalled carbon nanotubes doped with phosphorus (P) and nitrogen (N) are synthesized using a solution of ferrocene, triphenyl-phosphine, and benzylamine in conjunction with spray pyrolysis. We demonstrate that iron phosphide (Fe3P) nanoparticles act as catalysts during nanotube growth, leading to the formation of novel PN-doped multiwalled carbon nanotubes. The samples were examined by high resolution electron microscopy and microanalysis techniques, and their chemical stability was explored by means of thermogravimetric analysis in the presence of oxygen. The PN-doped structures reveal important morphology and chemical changes when compared to N-doped nanotubes. These types of heterodoped nanotubes are predicted to offer many new opportunities, in the fabrication of fast-response chemical sensors.://000254408000011 1936-0851ISI:00025440800001110.1021/nn700330w}F}?Kalinin, S. V. Meunier, V.20086Electronic flexoelectricity in low-dimensional systemsPhysical Review B773JanSymmetry breaking at surfaces and interfaces and the capability to support large strain gradients in nanoscale systems enable unusual forms of electromechanical coupling. Here, we introduce the concept of electronic flexoelectricity, a phenomenon that is manifested when the mechanical deformation of nonpolar quantum systems results in the emergence of net dipole moments and hence linear electromechanical coupling proportional to local curvature. The concept is illustrated in carbon systems, including polyacetylene and nanographitic ribbons. Using density functional theory calculations for systems made of up to 400 atoms, we determine the flexoelectric coefficients to be of the order of similar to 0.1e, in agreement with the prediction of linear theory. The implications of electronic flexoelectricity on electromechanical device applications and physics of carbon-based materials are discussed.://000252862900018 1098-0121ISI:000252862900018!033403 10.1103/PhysRevB.77.033403wF}?Meunier, V. Krstic, P. S.2008<Enhancement of the transverse conductance in DNA nucleotidesJournal of Chemical Physics1284Jan{We theoretically study the electron transport properties of DNA nucleotides placed in the gap between two single-wall carbon nanotubes capped or terminated with H or N. We show that in the case of C-cap and H-termination the current at low electric bias is dominated by nonresonant tunneling, similarly to the cases of gold electrodes. In nitrogen-terminated nanotube electrodes, the nature of current is primarily quasiresonant tunneling and is increased by several orders of magnitude. We discuss the consequence of our result on the possibility of recognition at the level of single molecule. (C) 2008 American Institute of Physics.://000252821200003 0021-9606ISI:000252821200003041103 10.1063/1.2835350}? 'Huang, J. S. Sumpter, B. G. Meunier, V.20087Theoretical model for nanoporous carbon supercapacitors520-524'Angewandte Chemie-International Edition473://000252452800013 1433-7851ISI:00025245280001310.1002/anie.200703864}? rSumpter, B. G. Meunier, V. Romo-Herrera, J. M. Cruz-Silva, E. Cullen, D. A. Terrones, H. Smith, D. J. Terrones, M.2007Nitrogen-mediated carbon nanotube growth: Diameter reduction, metallicity, bundle dispersability, and bamboo-like structure formation369-375Acs Nano14NovKCarbon nanotube growth in the presence of nitrogen has been the subject of much experimental scrutiny, sparking intense debate about the role of nitrogen in the formation of diverse structural features, including shortened length, reduced diameters, and bamboo-like multilayered nanotubules. In this paper, the origin of these features is elucidated using a combination of experimental and theoretical techniques, showing that N acts as a surfactant during growth. N doping enhances the formation of smaller diameter tubes. It can also promote tube closure which includes a relatively large amount of N atoms into the tube lattice, leading to bamboo-like structures. Our findings demonstrate that the mechanism is independent of the tube chirality and suggest a simple procedure for controlling the growth of bamboo-like nanotube morphologies.://000252267200022 1936-0851ISI:00025226720002210.1021/nn700143q}? QSumpter, B. G. Meunier, V. Valeev, E. F. Lampkins, A. J. Li, H. Castellano, R. K.2007#A new class of supramolecular wires 18912-18916Journal of Physical Chemistry C11151DecWe present an unconventional approach to the development of 1-D supramolecular wires based on the selfassembly of donor-sigma-acceptor molecules. The concept is demonstrated using one class of these systems, 1-aza-adamantanetriones (AATs), that are well-characterized in terms of their solution/solid-state self-assembly and chemical manipulation. Our results show that accompanying spontaneous organization of the molecules into 1-D periodic arrays is delocalization of the frontier molecular orbitals through the saturated tricyclic cores of the monomers that span the entire system. The electronic band structure for the 1-D wire reveals significant dispersion and can be tuned from the insulating regime to the semiconducting regime by suitable chemical functionalization of the core. The theoretical understanding of this new class of supramolecular structures sets the stage for the tailored design of novel functional materials that are an alternative to those comprised of traditional pi-conjugated systems.://000251830200018 1932-7447ISI:00025183020001810.1021/jp076329p0F}? !Latil, S. Meunier, V. Henrard, L.2007Massless fermions in multilayer graphitic systems with misoriented layers: Ab initio calculations and experimental fingerprintsPhysical Review B7620NovWe examine how the misorientation of a few stacked graphene layers affects the electronic structure of carbon nanosystems. We present ab initio calculations on bilayer and trilayer systems to demonstrate that the massless fermion behavior typical of single-layered graphene is also found in incommensurate multilayered graphitic systems. We also investigate the consequences of this property on experimental fingerprints, such as Raman spectroscopy and scanning tunneling microscopy (STM). Our simulations reveal that STM images of turbostratic few-layer graphite are sensitive to the layer arrangement. We also predict that the resonant Raman signals of graphitic samples are more sensitive to the orientation of the layers than to their number.://000251326900014 1098-0121ISI:000251326900014!201402 10.1103/PhysRevB.76.201402F}? :Amara, H. Latil, S. Meunier, V. Lambin, P. Charlier, J. C.2007aScanning tunneling microscopy fingerprints of point defects in graphene: A theoretical predictionPhysical Review B7611Sep{Scanning tunneling microscopy (STM) is one of the most appropriate techniques to investigate the atomic structure of carbon nanomaterials. However, the experimental identification of topological and nontopological modifications of the hexagonal network of sp(2) carbon nanostructures remains a great challenge. The goal of the present theoretical work is to predict the typical electronic features of a few defects that are likely to occur in sp(2) carbon nanostructures, such as atomic vacancy, divacancy, adatom, and Stone-Wales defect. The modifications induced by those defects in the electronic properties of the graphene sheet are investigated using first-principles calculations. In addition, computed constant-current STM images of these defects are calculated within a tight-binding approach in order to facilitate the interpretation of STM images of defected carbon nanostructures.://000249786400114 1098-0121ISI:000249786400114!115423 10.1103/PhysRevB.76.115423ghB?.Fuentes-Cabrera, M. Meunier, V. Sumpter, B. G.2007OBenzo-homologated nucleobases in a nanotube-electrode set-up for DNA sequencingNanotechnology1842Motivated by the possibility that the conductivity signatures of benzo-homologated DNA bases could be used to sequence DNA, we have investigated the conductivity properties of these bases when they are non-covalently sandwiched between two (5, 5) nanotube electrodes. It is found that these bases conduct poorly, making it very difficult to distinguish them. An analysis of the changes in the conductivity of benzo-adenine as a function of the distance between the tips of the nanotubes revealed that, even though the conductance increases by four orders of magnitude when the electrodes are brought closer together, the net conductance remains rather small. These results suggest that benzo-homologated bases, despite having smaller HOMO-LUMO gaps than their natural counterparts, when non-covalently bound to theCs(?Meunier, V. Sumpter, B. G.2007FTuning the conductance of carbon nanotubes with encapsulated molecules424032Nanotechnology1842vIt was recently shown that a molecule encapsulated inside a carbon nanotube can be used to devise a novel type of non-volatile memory element. At the heart of the mechanism for storing and reading information is the new concept of a molecular gate where the molecule acts as a passive gate that hinders the flow of electrons for a given position relative to the nanotube host. By systematically exploring the effects of encapsulation of an acceptor molecule in a series of carbon nanotubes, we show that the reliability of the memory mechanisN<?CSumpter, B. G. Meunier, V. Vazquez-Mayagoitia, A. Castellano, R. K.2007NInvestigation of the nanoscale self-assembly of donor-sigma-acceptor molecules 2233-2242*International Journal of Quantum Chemistry10712Electronic structure calculations are used to explore the nature of the interactions that lead to the self-assembly of a new class of functionalized donor-sigma-acceptor molecules, 1-aza-adamantanetriones (AATs), and the consequences of molecular structure on the resulting supramolecular systems. The results show how the self-assembly process originates from the saturated core of the molecules that underlies their shape, conformational preferences, and dipole-directed one-dimensional assembly. The solvation properties of the monomers are explored and H-1 NMR chemical shift values are determined and compared to experimental trends. A theoretical understanding of this class of supramolecular structures coupled with their molecular-level tunability introduces the possibility to des}?*Drummond, M. L. Meunier, V. Sumpter, B. G.2007?Structure and stability of small boron and boron oxide clusters 6539-6551Journal of Physical Chemistry A11128JulTo rationally design and explore a potential energy source based on the highly exothermic oxidation of boron, density functional theory (DFT) was used to characterize small boron clusters with 0-3 oxygen atoms and a total of up to ten atoms. The structures, vibrational frequencies, and stabilities were calculated for each of these clusters. A quantum molecular dynamics procedure was used to locate the global minimum for each species, which proved to be crucial given the unintuitive structure of many of the most stable isomers. Additionally, due to the plane-wave, periodic DFT code used in this study a straightforward comparison of these clusters to the bulk boron and B2O3 structures was possible despite the great structural and energetic differences between the two forms. Through evaluation of previous computational and experimental work, the relevant low-energy structures of all but one of the pure boron clusters can be assigned with great certainty. Nearly all of the boron oxide clusters are described here for the first time, but there are strong indications that the DFT procedure chosen is particularly well suited for the task. Insight into the trends in boron and boron oxide cluster stabilities, as well as the ultimate limits of growth for each, are also provided. The work reported herein provides crucial information towards understanding the oxidation of boron at a molecular level.://000247966600053 1089-5639ISI:00024796660005310.1021/jp0726182}?Souza, A. G. Meunier, V. Terrones, M. Sumpter, B. G. Barros, E. B. Villalpando-Paez, F. Mendes, J. Kim, Y. A. Muramatsu, H. Hayashi, T. Endo, M. Dresselhaus, M. S.2007\Selective tuning of the electronic properties of coaxial nanocables through exohedral doping 2383-2388 Nano Letters78Aug#The electronic properties of exohedrally doped double-walled carbon nanotubes (DWNTs) have been investigated using density functional theory and resonance Raman spectroscopy (RRS) measurements. First-principles calculations elucidate the effects of exohedral doping on the M@S and S@M systems, where a metallic (M) tube is either inside or outside a semiconducting (S) one. The results demonstrate that metallic nanotubes are extremely sensitive to doping even when they are inner tubes, in sharp contrast to semiconducting nanotubes, which are not affected by doping when the outer shell is a metallic nanotube (screening effects). The theoretical predictions are in agreement with RRS data on Br-2- and H2SO4-doped DWNTs. These results pave the way to novel nanoscale electronics via exohedral doping.://000248657800039 1530-6984ISI:00024865780003910.1021/nl0710351KF}?.Park, K. T. Pan, M. Meunier, V. Plummer, E. W.2007>Reoxidation of TiO2(110) via Ti interstitials and line defectsPhysical Review B7524Jun9The interaction of oxygen with line defects of Ti interstitials on a TiO2(110) surface is investigated using scanning tunneling microscopy (STM) measurements and first-principles calculations. Ab initio molecular dynamics calculations show that an oxygen molecule dissociatively adsorbs on a row of Ti interstitials. Oxygen atoms subsequently surround a Ti interstitial to form the equatorial plane of a partially complete octahedron, a basic building block for single- and double-strand formation. Upon the exposure of single strands to oxygen at room temperature, bright spots preferentially agglomerate on and along strands. The STM images of the bright spots, interpreted with density functional theory, indicate that they are TiOx (x < 2) aggregates and that strands may serve as nucleation sites for the surface growth.://000247625000114 1098-0121ISI:000247625000114!245415 10.1103/PhysRevB.75.245415s?\Bernholc, J. Lu, W. Nakhmanson, S. M. Hahn, P. H. Meunier, V. Nardelli, M. B. Schmidt, W. G.2007%Atomic scale design of nanostructures147-156MOLECULAR PHYSICS1052-3Recent advances in theoretical methods and high performance computing allow for reliable first-principles predictions of complex nanostructured materials and devices. This paper describes three examples: (i) non-equilibrium electron transport through molecular junctions, as a stepping stone for the design of molecular-scale devices and for integration of biomolecules with Si technology; (ii) polarization and piezoelectric properties of PVDF and related polymers; and (iii) the many-body optical spectrum of water. For the molecular junction, our results provide a qualitative picture and quantitative understanding of the mechanism leading to negative differential resistance for a large class of small molecules. For ferroelectric polymers, the calculations show that their polarization is described by cooperative, quantum-mechanical interactions between polymer chains. Nevertheless, the ab initio results lead to a simple parameterization of polarization as a function of copolymer concentration. Finally, our calculations explain the well-known redshift @}?ARomo-Herrera, J. M. Terrones, M. Terrones, H. Dag, S. Meunier, V.2007KCovalent 2D and 3D networks from 1D nanostructures: Designing new materials570-576 Nano Letters73MarWe show extensive theoretical studies related to the generation and characterization of 2D and 3D ordered networks using 1D units that are connected covalently. We experimentally created multi-terminal junctions containing 1D carbon blocks in order to study the most common morphologies and branched structures that could be used in the theoretical design of network models. We found that the mechanical and electronic characteristics of ordered networks based on carbon nanotubes (ON-CNTs) are dominated by their specific super-architecture (hexagonal, cubic, square, and diamond-type). We show that charges follow specific paths through the nodes of the multi-terminal systems, which could result in complex integrated nanoelectronic circuits. The 3D architectures reveal their ability to support extremely high unidirectional stress when their mechanical properties are studied. In addition, these networks are shown to perform better than standard carbon aerogels because of their low mass densities, continuous porosities, and high surface areas.://000244867400006 1530-6984ISI:00024486740000610.1021/nl0622202;F}?)Meunier, V. Kalinin, S. V. Sumpter, B. G.2007cNonvolatile memory elements based on the intercalation of organic molecules inside carbon nanotubesPhysical Review Letters985FebWe propose a novel class of nonvolatile memory elements based on the modification of the transport properties of a conducting carbon nanotube by the presence of an encapsulated molecule. The guest molecule has two stable orientational positions relative to the nanotube that correspond to conducting and nonconducting states. The mechanism, governed by a local gating effect of the molecule on the electronic properties of the nanotube host, is studied using density functional theory. The mechanisms of reversible reading and writing of information are illustrated with a F(4)TCNQ molecule encapsulated inside a metallic carbon nanotube. Our results suggest that this new type of nonvolatile memory element is robust, fatigue-free, and can operate at room temperature.://000244646100051 0031-9007ISI:000244646100051$056401 10.1103/PhysRevLett.98.056401r(?1Meunier, V. Lu, W. C. Sumpter, B. G. Bernholc, J.2006KDensity functional theory studies of quantum transport in molecular systems 3334-3342*International Journal of Quantum Chemistry10615Conventional semiconducting devices are rapidly approaching their physical limits, encouraging an increasing number of researchers across multiple disciplines to attempt to devise innovative ways to decrease the size and increase the performance of critical features in microelectronic circuits. One possible route is based on the idea of using molecules and molecular structures as functional electronic devices. While impressive experimental progress toward the realization of molecular electronics has been achieved, full insight into the potential for molecular-based electronics requires accurate theoretical investigations of the processes governing their functioning. In the present study, we show that large-scale quantum electronic structure calculations coupled with nonequilibrium Green function theory can be employed to determine quantum conductance on practical length scales. The combination of state-of-the-art quantum mechanical methods, efficient numerical algorithms, and high-performance computing allows for realistic evaluation of properties at length scales that are routinely reached experimentally. Two illustrations of the method are presented. First, we investigate the electron transport properties of a Si/organic-molecule/Si junction, using a numerically optimized basis. Second, quantum chemical calculations using up to 10(4) basis functions are carried out to iwF}?zZhou, J. Dag, S. Senanayake, S. D. Hathorn, B. C. Kalinin, S. V. Meunier, V. Mullins, D. R. Overbury, S. H. Baddorf, A. P.2006Adsorption, desorption, and dissociation of benzene on TiO2(110) and Pd/TiO2(110): Experimental characterization and first-principles calculationsPhysical Review B7412SepAdsorption and reaction of benzene molecules on clean TiO2(110) and on TiO2(110) with deposited Pd nanoparticles are investigated using a combination of scanning tunneling microscopy (STM), temperature-programmed desorption, and first-principles calculations. Above similar to 50 K, the one-dimensional motion of benzene between bridging oxygen rows is shown to be too fast for STM imaging. At 40 K benzene molecules form chains on top of titanium rows, with calculations indicating every other benzene is rotated 30 degrees. Both experimental and theoretical studies find no dissociative reactivity of benzene on the clean TiO2(110) surface, due to little hybridization between TiO2 and benzene electronic states. After deposition of Pd nanoparticles, molecular benzene is observed with STM both on the substrate and adjacent to metallic particles. Upon heating to 800 K, benzene fully breaks down into its atomic constituents in a multistep decomposition process.://000240872500067 1098-0121ISI:000240872500067!125318 10.1103/PhysRevB.74.125318 nvestigate amphoteric doping of carbon nanotubes by encapsulation of organic molecules. (c) 2006 Wiley Periodicals, Inc.://000241642400033 ISI:00024164240003310.1002/qua.21197 !Hhe energetics of the pentagon-hep m is very sensitive to the interaction between the nanotube host and the molecule guest.://000249735800033 ISI:00024973580003310.1088/0957-4484/18/42/424032PF}?(Park, K. Pan, M. Meunier, V. Plummer, E.20068Surface reconstructions of TiO2(110) driven by suboxidesPhysical Review Letters9622JunAScanning tunneling microscopy and density functional theory are used to develop a new structural model for surface reconstructions driven by Ti interstitials on TiO2(110). Ti interstitials form the edge- or face-sharing octahedra that serve as building blocks for (1x1) reconstruction. Thus, contrary to conventional wisdom, the 1x1 periodicity is insufficient to establish the correct surface stoichiometry. Furthermore, in our structural and compositional model the reversible oxidation or reduction between (1x1) and (1x2) is entirely achieved by transfer of the added rows.://000238161400039 0031-9007ISI:000238161400039$226105 10.1103/PhysRevLett.96.226105]F}?5Rodriguez, B. J. Jesse, S. Meunier, V. Kalinin, S. V.2006eScanning frequency mixing microscopy of high-frequency transport behavior at electroactive interfacesApplied Physics Letters8814Apr An approach for high-frequency transport imaging, referred to as scanning frequency mixing microscopy (SFMM), is developed. Application of two high-frequency bias signals across an electroactive interface results in a low-frequency component due to interface nonlinearity. The frequency of a mixed signal is chosen within the bandwidth of the optical detector and can be tuned to the cantilever resonances. The SFMM signal is comprised of an intrinsic device contribution and a capacitive mixing contribution, and an approach to distinguish the two is suggested. This technique is illustrated on a model metal-semiconductor interface. The imaging mechanism and surface-tip contrast transfer are discussed. SFMM allows scanning probe microscopy based transport measurements to be extended to higher, ultimately gigahertz, frequency regimes, providing information on voltage derivatives of interface resistance and capacitance, from which device characteristics such as Schottky barrier height, etc., can be estimated. (c) 2006 American Institute of Physics.://000236612000102 0003-6951ISI:000236612000102143128 10.1063/1.2192977cF}?"Lu, W. C. Meunier, V. Bernholc, J.2005KNonequilibrium quantum transport properties of organic molecules on siliconPhysical Review Letters9520NovGElectron transport properties of a Si/organic-molecule/Si junction are investigated by large-scale nonequilibrium Green function calculations. The results provide a qualitative picture and quantitative understanding of the importance of self-consistent screening, broadening of quasimolecular orbitals under large bias, and enhancement of transmission, which occurs when the broadened lowest unoccupied molecular orbital aligns with the conduction band edge of the negative lead. The varying coupling can lead to negative differential resistance for a large class of small molecules.://000233243500051 0031-9007ISI:000233243500051$206805 10.1103/PhysRevLett.95.206805F}?Meunier, V. Sumpter, B. G.2005zAmphoteric doping of carbon nanotubes by encapsulation of organic molecules: Electronic properties and quantum conductanceJournal of Chemical Physics1232JulhIn order to investigate and optimize the electronic transport processes in carbon nanotubes doped with organic molecules, we have performed large-scale quantum electronic structure calculations coupled with a Green's function formulation for determining the quantum conductance. Our approach is based on an original scheme where quantum chemistry calculations on finite systems are recast to infinite, nonperiodic (i.e., open) systems, therefore mimicking actual working devices. Results from these calculations clearly suggest that the electronic structure of a carbon nanotube can be easily manipulated by encapsulating appropriate organic molecules. Charge transfer processes induced by encapsulated organic molecules lead to efficient n- and p-type doping of the carbon nanotube. Even though a molecule can induce p and n doping, it is shown to have a minor effect on the transport properties of the nanotube as compared to a pristine tube. This type of doping therefore preserves the intrinsic properties of the pristine tube as a ballistic conductor. In addition, the efficient process of charge transfer between the organic molecules and the nanotube is shown to substantially reduce the susceptibility of the pi electrons of the nanotube to modification by oxygen while maintaining stable doping (i.e., no dedoping) at room temperature. (c) 2005 American Institute of Physics.://000230653700032 0021-9606ISI:000230653700032024705 10.1063/1.1931547?Biro, L. P. Mark, G. I. Koos, A. A. Horvath, Z. E. Szabo, A. Fonseca, A. Nagy, J. B. Colomer, J. F. Lambin, P. Meunier, V. Charlier, J. C. Bedoya-Martinez, O. N. Hernandez, E.2005!Regularly curved carbon nanotubes523-5330FULLERENES NANOTUBES AND CARBON NANOSTRUCTURES 13523-533The increasing number of reports on regularly curved carbon nanotube-type architectures makes it increasingly important to understand the structure of these nano-objects, to predict their properties, and to get insight in the way they form. The present work attempts to explore some properties of regularly curved carbon nanotube by combiningF}? BMeunier, V. Kalinin, S. V. Shin, J. Baddorf, A. P. Harrison, R. J.2004Quantitative analysis of electronic properties of carbon nanotubes by scanning probe microscopy: From atomic to mesoscopic length scalesPhysical Review Letters9324Dec}A new multiscale approach to the quantitative interpretation of scanning probe microscopy data in terms of the local electronic properties of 1D systems such as carbon nanotubes is presented. The interactions between a probe and the system are treated using a combination of first-principles density functional calculations and continuum electrostatics modeling. Realistic tip size effects are included using an image charge model. It is shown that the local potential at a nanotube on a substrate due to a probe can be calculated quantitatively, allowing experimental data to be analyzed in terms of the electronic structure of defects.://000225661100062 0031-9007ISI:000225661100062$246801 10.1103/PhysRevLett.93.246801}?!:Bernholc, J. Nakhmanson, S. M. Nardelli, M. B. Meunier, V.2004=Understanding and enhancing polarization in complex materials12-21"Computing in Science & Engineering66Nov-DecRecent advances in theoretical methods and high-performance computing allow for reliable first-principles investigations of complex materials. This article focuses on calculating and predicting the properties of piezoelectrics and "designing" new materials with enhanced piezoelectric responses. The authors consider two systems: boron-nitride nanotubes (BNNTs) and polymers in the polyvinylidene fluoride (PVDF) family.://000224626000005 1521-9615ISI:000224626000005&}?"2Shin, J. Meunier, V. Baddorf, A. P. Kalinin, S. V.2004<Nonlinear transport imaging by scanning impedance microscopy 4240-4242Applied Physics Letters8518NovScanning probe microscopy is an established tool for characterization of the linear static and frequency-dependent lateral electronic transport in materials and devices at the nanoscale. In this letter, a modified scanning impedance microscopy (SIM) technique is proposed to extend the nanoscale transport measurements of intrinsic material properties to the nonlinear regime, through detection of frequency harmonics, and exemplified by a detailed study of a prototypical metal-semiconductor interface. The imaging mechanism, surface-tip contrast transfer, optimal experimental conditions, and potential applications of nonlinear SIM are discussed. This technique can be readily transferred to most cantilever-based scanning probe microscopes. (C) 2004 American Institute of Physics.://000224894900095 0003-6951ISI:00022489490009510.1063/1.1812372}?#Meunier, V. Lambin, P.20042Scanning tunnelling microscopy of carbon nanotubes 2187-2203qPhilosophical Transactions of the Royal Society of London Series a-Mathematical Physical and Engineering Sciences3621823OctThis paper briefly reviews how scanning tunnelling microscopy (STM) and spectroscopy (STS) are used to analyse the atomic structure and the electronic properties of individual single-wall carbon nanotubes. In this area, the progress accomplished over the past several years has been spectacular. As this paper demonstrates, all the effects predicted by theory have been verified experimentally. Geometrical and electronic effects specific to carbon nanotubes are illustrated by analysing a series of STM images and STS spectra computed using a tight-binding theory. The simulations include a catalogue of images of 27 single-wall nanotubes, Stone-Wales defects in semiconducting nanotubes, and a symmetric Y-junction.://000224557900009 1364-503XISI:00022455790000910.1098/rsta.2004.1435}?$VRocquefelte, X. Rignanese, G. M. Meunier, V. Terrones, H. Terrones, M. Charlier, J. C.2004iHow to identify Haeckelite structures: A theoretical study of their electronic and vibrational properties805-810 Nano Letters45MayFirst-principles (FP) calculations of the electronic and vibrational properties of three different Haeckelite structures have been performed. The relatively low cohesive energies (when compared to C-60) of these phases suggest the possible synthesis of such novel carbon arrangements. In agreement with previous tight-binding calculations (Terrones, H.; Terrones, M.; Hernandez, E.; Grobert, N.; Charlier, J.-C.; Ajayan, P. M. Phys. Rev. Lett. 2000, 84, 1716), the Haeckelite structures exhibit a clear metallic behavior. In addition, within the ab initio framework, we predict the IR and Raman frequencies, which constitute the fingerprint of their structure and allow for their unambiguous identification. STM images and quantum conductances of various tubular Haeckelite structures are also calculated within a tight-binding framework. The three investigated Haeckelite structures are shown to be good candidates of conducting wires with great potential in nanoelectronics. The results presented here provide a catalog of properties that will aid in the identification of other Haeckelite structures as well as carbon systems containing pentagonal and heptagonal defects.://000221410000009 1530-6984ISI:00022141000000910.1021/nl049879x?%.Lambin, P. Mark, G. I. Meunier, V. Biro, L. P.2003-Computation of STM images of carbon nanotubes493-503*International Journal of Quantum Chemistry954-5 Scanning tunneling microscopy (STM) is the only probing technique that allows for the investigation of both the topography and the electronic structure of carbon nanosystems at a subnanometer resolution. The interpretation of the STM images of carbon nanostructures involves complications that are normally absent in the study of planar crystalline surfaces. The complications typically appear from a number of quantum effects responsible for distortions in the microscope image of a nano-object. Because of these difficulties, computer simulation plays an extremely important role in the analysis of experimental data. In the current article, we report on two theoretical approaches developed for aiding in the interpretation and understanding of the formation of the STM image of a nanotube: first, the quantum mechanical dynamics of a wave packet, which allows for the modeling of the flow of the tunneling current between a tip and a nanotube supported by a substrate; and, second, a tight-binding perturbation theory that allows for the explicit calculation of realistic STM images and scanning tunneling spectra of carbon nanostructures. An atlas of computed STM }?&xHernandez, E. Meunier, V. Smith, B. W. Rurali, R. Terrones, H. Nardelli, M. B. Terrones, M. Luzzi, D. E. Charlier, J. C.2003DFullerene coalescence in nanopeapods: A path to novel tubular carbon 1037-1042 Nano Letters38AugzA fascinating structural transformation occurring inside single-walled carbon nanotubes (SWNTs) is the fullerene coalescence, which is responsible for forming stable zeppelinlike carbon molecules. We report in situ transmission electron microscope (TEM) observations revealing sequences of fullerene coalescence induced by electron irradiation on pristine nanotube peapods, together with extensive theoretical investigations of the microscopic mechanism underlying this process. TEM images indicate that the merging of fullerenes results in stable but corrugated tubules (5 to 7 Angstrom in diameter) confined within SWNTs. These observations have been confirmed using a combination of theoretical approaches based on molecular dynamics, empirical potentials, tight-binding methods, Monte Carlo techniques, and first principles calculations. We have fully elucidated the coalescence mechanism of fullerenes inside SWNTs under electron irradiation and thermal annealing. The process occurs via the polymerization Of C-60 molecules followed by surface reconstruction, which can be triggered either by the formation of vacancies (created under electron irradiation) or by surface-energy minimization activated by thermal annealing. These novel tubular forms of carbon contain hexagons, pentagons, heptagons, and octagons. The stability, electronic properties, and electron conductance of the novel tubules are strongly affected by the final geometry of the coalesced fullerene complex. The possibility of forming highly conducting and semiconducting tubular structures suggests new avenues in designing carbon nanowires with specific electronic characteristics.://000184892400010 1530-6984ISI:00018489240001010.1021/nl034283fo}?'EMeunier, V. Nardelli, M. B. Bernholc, J. Zacharia, T. Charlier, J. C.2003Response to "Comment on 'Intrinsic electron transport properties of carbon nanotube Y junctions' " [Appl. Phys. Lett. 83, 1674 (2003)] 1676-1677Applied Physics Letters838Aug://000184844100061 0003-6951ISI:00018484410006110.1063/1.1604949[F}?(HNakhmanson, S. M. Calzolari, A. Meunier, V. Bernholc, J. Nardelli, M. B.2003HSpontaneous polarization and piezoelectricity in boron nitride nanotubesPhysical Review B6723Jun%Ab initio calculations of the spontaneous polarization and piezoelectric properties of boron nitride nanotubes show that they are excellent piezoelectric systems with response values larger than those of piezoelectric polymers. The intrinsic chiral symmetry of the nanotubes induces an exact cancellation of the total spontaneous polarization in ideal, isolated nanotubes of arbitrary indices. Breaking of this symmetry by intertube interaction or elastic deformations induces spontaneous polarization comparable to those of wurtzite semiconductors.://000184040700074 1098-0121ISI:000184040700074!235406 10.1103/PhysRevB.67.235406}?)EMeunier, V. Nardelli, M. B. Bernholc, J. Zacharia, T. Charlier, J. C.2002FIntrinsic electron transport properties of carbon nanotube Y-junctions 5234-5236Applied Physics Letters8127Dec`The electron transport properties of three-terminal carbon-nanotube junctions are investigated within the Landauer theory of quantum conductance. Using a realistic tight-binding Hamiltonian, we demonstrate that the experimentally observed rectifying behavior is not an intrinsic property of the junction, but rather of the contact geometry. When semiconducting nanotubes are connected to metallic leads, nontransmitting states are induced at the nanotube-metal interface, leading to asymmetric transmission curves and potentially rectifying behavior of the nanodevice. (C) 2002 American Institute of Physics.://000180160800046 0003-6951ISI:00018016080004610.1063/1.1533842}?*Charlier, J. C. Terrones, M. Baxendale, M. Meunier, V. Zacharia, T. Rupesinghe, N. L. Hsu, W. K. Grobert, N. Terrones, H. Amaratunga, G. A. J.2002<Enhanced electron field emission in B-doped carbon nanotubes 1191-1195 Nano Letters211Nov$Field emission properties of B-doped carbon nanotubes are investigated from both theoretical and experimental standpoints. Using tight-binding and ab initio calculations, it is observed that B-saturating tip edges of carbon nanotubes induce the presence of large peaks within the local density of states (LDOS) located in an energy region close to the Fermi level (Ef). These localized states suggest a field emission enhancement for the B-doped tubes. In addition, ab initio theoretical results indicate that the work function for B-doped tubes is 1.7 eV lower when compared to pure carbon-terminated nanotubes. Experimentally, it is found that B-doped tubes, which are produced by arc discharge techniques and contain B mainly at the tips, exhibit stable electron field emission at lower turn-on voltages (1.4 V/mum) when compared to pure single- and multiwalled carbon nanotubes (2.8 and 3.0 V/mum, respectively) measured under the same conditions. We strongly believe our results will bring new insights in the fabrication of stable field emission sources.://000179301800003 1530-6984ISI:00017930180000310.1021/nl0256457 }?+?Bernholc, J. Brenner, D. Nardelli, M. B. Meunier, V. Roland, C.20021Mechanical and electrical properties of nanotubes347-375#Annual Review of Materials Research32qWe review the recent progress in our understanding of the mechanical and electrical properties of carbon nanotubes, emphasizing the theoretical aspects. Nanotubes are the strongest materials known, but the ultimate limits of their strength have yet to be reached experimentally. Modeling of nanotube-reinforced composites indicates that the addition of small numbers of nanotubes may lead to a dramatic increase in the modulus, with only minimal crosslinking. Deformations in nanotube structures lead to novel structural transformations, some of which have clear electrical signatures that can be utilized in nanoscale sensors and devices. Chemical reactivity of nanotube walls is facilitated by strain, which can be used in processing and functionalization. Scanning tunneling microscopy and spectroscopy have provided a wealth of information about the structure and electronic properties of nanotubes, especially when coupled with appropriate theoretical models. Nanotubes are exceptional ballistic conductors, which can be used in a variety of nanodevices that can operate at room temperature. The quantum transport through nanotube structures is reviewed at some depth, and the critical roles played by band structure, one-dimensional confinement, and coupling to nanoscale contacts are emphasized. Because disorder or point defect-induced scattering is effectively averaged over the circumference of the nanotube, electrons can propagate ballistically over hundreds of nanometers. However, severe deformations or highly resistive contacts isolate nanotube segments and lead to the formation of quantum dots, which exhibit Coulomb blockade effects, even at room temperature. Metal-nanotube and nanotube-nanotube contacts range from highly transmissive to very resistive, depending on the symmetry of two structures, the charge transfer, and the detailed rehybridization of the wave functions. The progress in terms of nanotube applications has been extraordinarily rapid, as evidenced by the development of several nanotube-based prototypical devices, including memory and logic circuits, chemical sensors, electron emitters and electromechanical actuators.://000177827600015 1531-7331ISI:000177827600015'10.1146/annurev.matsci.32.112601.134925}?,*Oh, J. Meunier, V. Ham, H. Nemanich, R. J.2002:Single electron tunneling of nanoscale TiSi2 islands on Si 3332-3337Journal of Applied Physics926SepNanoscale TiSi2 islands are formed by electron beam deposition of a few monolayers of titanium on an atomically clean silicon surface followed by in situ annealing at high temperatures (800-1000 degreesC). The lateral diameter of typical islands are similar to5 nm, and they form a nanoscale metal-semiconductor interface. Direct probing of the electrical characteristics of these islands on both p- and n-type Si substrates was performed using ultrahigh vacuum scanning tunneling microscopy and scanning tunneling spectroscopy. With the vacuum between the tip and the island as a second tunnel junction, we thus form a double-junction system for observation of single electron tunneling (SET) effects. Moreover, the small dimensions of the system allow room temperature observation. The results showed features in the I-V spectra attributed to single electron tunneling. Features were more evident when the island-Si junction was in reverse bias. For substrates with a thin epitaxial layer of intrinsic Si, the tunneling related features were enhanced for both doping types. The experimental results are compared with the standard theory and numerical values from the fitting are in agreement with the experimental structures. The results indicate that the nanoscale Schottky barrier of the island-substrate interface can be employed as a tunnel barrier in SET structures. (C) 2002 American Institute of Physics.://000177683000059 0021-8979ISI:00017768300005910.1063/1.1499531F}?-)Roland, C. Meunier, V. Larade, B. Guo, H.2002/Charge transport through small silicon clustersPhysical Review B663JulWith a recently developed ab initio nonequilibrium Green's-function formalism, we have investigated the transport behavior of small Si-n, n=1-10, 13, and 20 nanoclusters between atomistic Al and Au leads. All of the clusters display metallic I-V characteristics, with typical conductances ranging between two and three (units of G(o)=2e(2)/h). The transport properties of these cluster junctions may be understood in terms of both the band structure of the electrodes, and the molecular electronic states of the clusters as modified by the lead environment. In addition, the quantum transport properties of Si nanoclusters doped with a Na atom are also analyzed.://000177338500094 1098-0121ISI:000177338500094!035332 10.1103/PhysRevB.66.035332}?.GSimonis, P. Goffaux, C. Thiry, P. A. Biro, L. P. Lambin, P. Meunier, V.2002)STM study of a grain boundary in graphite319-322Surface Science5111-3JunA grain boundary in highly oriented pyrolitic graphite has been investigated by scanning tunneling microscopy (STM). Along the boundary, a periodic structure has been observed. Crystallographic models have been constructed in order to explain the bonding between the two grains and STM theoretical simulations have been carried out. They conclude to the probable presence of pentagon heptagon chains at the boundary. (C) 2002 Elsevier Science B.V. All rights reserved.://000176584000036 0039-6028ISI:000176584000036}?/3Meunier, V. Roland, C. Bernholc, J. Nardelli, M. B.2002WElectronic and field emission properties of boron nitride/carbon nanotube superlattices46-48Applied Physics Letters811JulBN/C nanotube superlattices are quasi one-dimensional heterostructures that show unique physical properties derived from their peculiar geometry. Using state-of-the-art ab initio calculations, we show that BN/C systems can be used for effective band-offset nanodevice engineering, polarization-based devices, and robust field emitters with an efficiency enhanced by up to two orders of magnitude over carbon nanotube systems. (C) 2002 American Institute of Physics.://000176426000016 0003-6951ISI:00017642600001610.1063/1.1491013PF}?0/Meunier, V. Kephart, J. Roland, C. Bernholc, J.2002HAb initio investigations of lithium diffusion in carbon nanotube systemsPhysical Review Letters887Feb+Li-nanotube systems can substantially improve the capacity of Li-ion batteries by utilizing both nanotube exteriors and interiors. Our ab initio simulations show that while Li motion through the sidewalls is forbidden, Li ions can enter tubes through topological defects containing at least nine-sided rings, or through the ends of open-ended nanotubes. Once inside, their motion is not diffusion limited. These results suggest that "damaging" nanotube ropes by either chemical or mechanical means will yield superior material for electrochemical storage.://000174021100043 0031-9007ISI:000174021100043$075506 10.1103/PhysRevLett.88.075506,}?13Meunier, V. Nardelli, M. B. Roland, C. Bernholc, J.2001>Structural and electronic properties of carbon nanotube tapersart. no.-195419Physical Review B6419NovCarbon nanotube tapers are a set of nanostructures comprised of straight tubular sections with decreasing diameters, joined to each other via conical funnels and terminated with a hemispherical cap. The funnels are formed with the help of topological defects, which minimally include at least one pentagon-heptagon pair. The structural, electronic, and transport properties of tapers are analyzed using realistic tight-binding models. Specifically, it is shown that straight nanotube tapers are monochiral objects. Among a variety of possible taper structures, kinetics of the growth process suggests that the most prevalent tapers will have either zigzag or armchair structures. Their scanning tunneling microscopy (STM) images have been simulated for identification purposes. The STM images of tapers are dominated by a protruding pentagon inherent in the taper structure, which unfortunately does not allow for an easy identification of the chirality of the underlying nanotubes. Turning to transport properties, it is shown that zigzag-based tapers will likely be poor conductors, because of gaps induced by the semiconducting segments. Armchair-based tapers, on the other hand, are characterized by a finite conductance at low bias voltages and make attractive prototypes for nanoscale probes and devices.://000172307900134 1098-0121ISI:000172307900134195419}?2 Lambin, P. Meunier, V. Rubio, A.20003Electronic structure of polychiral carbon nanotubes 5129-5135Physical Review B628Aug(Most of the works devoted so far to the electronic band structure of multiwall nanotubes have been restricted to the case in which the individual layers have the same chirality. By comparison, much less is known on the electronic properties of multiwall nanotubes that mix different chiralities. These are interesting systems, however, since they can be composed of both metallic and semiconducting layers. For the present work, tight-binding calculations were undertaken for polychiral two-layer nanotubes such as (9,6)@(15,10), (6,6)@(18,2), and others. The recursion technique was used to investigate how the densities of states of the individual layers are affected by the intertube coupling. Constant-current scanning-tunneling-microscopy (STM) images were also calculated for these systems. The result obtained is that the image of a two-wall nanotube is pretty much the same as that of the isolated external layer. It is only in the case of monochiral, commensurate structures such as (5,5)@(10,10) that interlayer effects can be seen in the STM topography.://000089003200053 0163-1829ISI:0000890032000531}?3/Lambin, P. Meunier, V. Henrard, L. Lucas, A. A.2000*Measuring the helicity of carbon nanotubes 1713-1721Carbon3811-12XMost of the properties of a single-wall nanotube depend on its diameter and, to a less extend, on its chiral angle also called the helicity of the structure. These two parameters, diameter and helicity, completely define the pair of Hamada indices (n, m) that characterize the atomic structure of a nanotube. The most powerful techniques that may give access to both diameter and helicity are STM and electron diffraction. Both techniques are reviewed in this paper. Emphasis is also given to the characterization of ropes of single-wall nanotubes. (C) 2000 Elsevier Science Ltd. All rights reserved.://000089028500025 0008-6223ISI:000089028500025}?4Meunier, V. Lambin, P.2000YScanning tunneling microscopy and spectroscopy of topological defects in carbon nanotubes 1729-1733Carbon3811-12Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are powerful techniques for investigating the electronic and topographic properties of carbon nanotubes. The growing availability of STM data allows the accurate study of perfect tubules. Today, the identification of topological and non-topological modifications of the hexagonal lattice of a carbon nanotube is experimentally challenging. Our recently proposed approach to interpret and predict STM and STS observations on a routine basis is used to simulate the topographic and spectroscopic signatures of pentagons and heptagons and contribute to their identification. (C) 2000 Elsevier Science Ltd. All rights reserved.://000089028500027 0008-6223ISI:000089028500027}?57Adessi, C. Devel, M. Binh, V. T. Lambin, P. Meunier, V.2000Influence of structural defects on Fresnel projection microscope images of carbon nanotubes: Implications for the characterization of nanoscale devices 13385-13388Physical Review B6120May^We report first quantum theoretical simulations of Fresnel type electronic diffraction images of carbon nanotubes junctions. These three-dimensional simulations are used to interpret fine features of experimental Fresnel projection microscope (FPM) images. The relevance of the FPM to observe nanodevices made from carbon nanotubes is then discussed.://000087284900017 0163-1829ISI:000087284900017}?6/Venema, L. C. Meunier, V. Lambin, P. Dekker, C.2000GAtomic structure of carbon nanotubes from scanning tunneling microscopy 2991-2996Physical Review B614JanThe atomic structure of a carbon nanotube can be described by its chiral angle and diameter and can be specified by a pair of lattice indices (n,m). The electronic and mechanical properties are critically dependent on these indices, Scanning tunneling microscopy (STM) is a useful tool to investigate carbon nanotubes since the atomic structure as well as the electronic properties of individual molecules can be determined. This paper presents a discussion of the technique to obtain (n,m) indices of nanotubes from STM images in combination with current-voltage tunnel spectra. image contrast, distortion effects, and determination of chiral angle and diameter are discussed. The procedure of(n,m) identification is demonstrated for a few single-walled carbon nanotubes.://000085348300085 1098-0121ISI:000085348300085Vr?7JMeunier, V. Lambin, P.19992Structural properties of carbon nanotube junctions667-675CANADIAN JOURNAL OF PHYSICS 779=The junction between two different nanotubes can be realized by the simple insertion of a pentagon-heptagon pair defect while preserving the triple coordination of each C atom. This insertion bends the structure to an angle depending on the distance between the pentagon and heptagon. The atomic structure of several of these junctions was optimized with the help of empirical potentials, the nanotubes on both sides of the junctions being considered as infinitely long. Local densities of sigma + pi electronic states were evaluated in the interfacial regions from a tight-binding Hamiltonian. From there, the electronic energy of these junctions was calculated and compared with that of the isolated nanotubes. It was established that the energy associated with the pentagon-heptagone pair in a graphitic tubule is of the order of 6 eV. An automatic generation algorithm for connecting any two tubules was developed. By restricting the Hamiltonian to the sole pi orbitals, this algorithm made it feasible to study t}?8 Meunier, V. Senet, P. Lambin, P.1999gScanning tunneling spectroscopy signature of finite-size and connected nanotubes: A tight-binding study 7792-7795Physical Review B6011SepWe present tight-binding-based simulations of the scanning tunneling spectroscopic signal of different types of carbon nanotubes. Capped, finite, and connected nanotubes have been investigated. We have computed scanning tunneling spectroscopy (STS) maps of each nanotube on different parts of the systems for various tip-sample bias potentials. STS reflects the electronic structure, which depends on the arrangement of atoms in the systems, and can be drastically different even for similar geometries. The computations are in good agreement with recently measured STS spectra. Furthermore, the STS spectra of pentagon and heptagon, which are needed for connecting different carbon nanotubes, constitute characteristic marks of topological defects.://000083070600032 0163-1829ISI:000083070600032k?9JHumbert, C. Buck, M. Calderone, A. Vigneron, J. P. Meunier, V. Champagne, B. Zheng, W. Q. Tadjeddine, A. Thiry, P. A. Peremans, A.1999In situ monitoring of the self-assembly of p-nitroanilino terminated thiol on gold: a study by IR-vis sum-frequency generation spectroscopy129-136*PHYSICA STATUS SOLIDI A-APPLIED RESEARCH 1751~We report on a vibrational study of the self-assembly of para-nitroanilino-dodecane-thiol (p-NAT, NO2-C6H4-NH-(CH2)(12)-SH) molecules an polycrystalline gold surfaces, by means of sum-frequency generation (SFG). In the investigated spectral range (1150 to 1400 cm(-1)), the evolution of the vibrational fingerprint indicates that important reorientations of the molecules occur during film growth, until a stable conformation is reached slightly before saturation coverage. The experimental data are interpreted with the help of ab initio calculations f}?:Lambin, P. Meunier, V.1999?Structural properties of junctions between two carbon nanotubes263-2660Applied Physics a-Materials Science & Processing683MarThe junction between two different nanotubes can be realized with the insertion of a single pentagon-heptagon pair in the honeycomb network. This defect bends the structure at an angle that depends on the distance between the pentagon and heptagon. The atomic structure of several junctions was optimized with the help of empirical potentials, the nanotubes on both sides of the junctions being considered as infinitely long. Local densities of sigma + pi electron states were evaluated in the interfacial region with a tight-binding Hamiltonian. From there, the electronic energy of these junctions was calculated and compared to that of the isolated nanotubes. It was established that the energy associated with the pentagon-heptagon pair in a graphitic tubule is of the order of 6 eV. An automatic algorithm for connecting any two tubules was developed. By restricting the Hamiltonian to the sole pi electrons, this algorithm made it feasible to study the energetics of the pentagon-heptagon defect in a systematic way.://000078993300001 0947-8396ISI:000078993300001}?;Meunier, V. Lambin, P.1998>Tight-binding computation of the STM image of carbon nanotubes 5588-5591Physical Review Letters8125DecSTM imaging of single-wall carbon nanotubes has recently been achieved with atomic resolution, revealing the chirality of the carbon network. In this work, a theoretical modeling of scanning tunneling microscopy of the nanotubes is presented, based on a tight-binding pi-electron Hamiltonian. This theory is simple enough to be used routinely for the computation of STM images and current-voltage characteristics, making it possible to investigate specific effects of the network curvature and topology such as a pentagon-heptagon pair defect.://000077659500028 0031-9007ISI:000077659500028c?<J"Lambin, P. Meunier, V. Biro, L. P.1998FElastic deformation of a carbon nanotube adsorbed on a stepped surface701-704Carbon365Carbon nanotubes prepared by thermal decomposition of acetylene on cobalt catalysts were investigated by scanning tunnelling microscopy (STM). One of the STM images revealed a nanotube with a diameter ca 1 nm getting over atomic steps on the (HOPG) graphite substrate on which the samples were deposited. The deformation and the stresses in this nanotube were evaluated from continuous-medium elasticity, using 12-6 C-C pair potentials to describe the interaction with the substrate. A good agreement was found between the computed shape of the deformed nanotube and that revealed by the STM. The calculations also indicated that the stresses only slowly increased with increasing step height and, for that reason, a nanotube adsorbed on a surface can get over sharp steps a few nanometres high without breaking. This result attests to the high flexibility of the carbon nanotube. (C) 19}?=#Meunier, V. Lambin, P. Lucas, A. A.1998?Atomic and electronic structures of large and small carbon tori 14886-14890Physical Review B5723JunThe stability of large carbon tori is examined within the elasticity theory. Tori of diameter larger than 200 nm obtained by bending a single-wall nanotube and connecting the two ends together are proved to be stable. Molecular mechanics is used for optimizing the structure of a small polygonal torus (C-1960) Obtained by connecting short portions of (6,6) and (10,0) nanotubes with ten pairs of pentagons and heptagons. The electronic structures of both small and large tori are determined within the framework of a tight-binding Hamiltonian, and their energies are compared. By application of London theory, it is shown that a magnetic field deeply influences the electronic structure of the carbon tori.://000074273500054 0163-1829ISI:000074273500054}?>"Meunier, V. Henrard, L. Lambin, P.1998#Energetics of bent carbon nanotubes 2586-2591Physical Review B574Jan1Several junctions between different nanotubes have been constructed which preserve the C sp(2) honeycomb lattice with the sole insertion of a pentagon and a heptagon. This construction bends the structure at an angle that depends on the distance between the pentagon and heptagon. The atomic structure of these systems was optimized with empirical interatomic potentials. The nanotubes on both sides of the junctions were treated as infinitely long. Local sigma+pi electron densities of states were computed locally in the interfacial region with a tight-binding Hamiltonian. From this, the electron energy of the junctions was computed and compared to that of the separated nanotubes. It is found that the energy of a pentagon-heptagon defect in the graphitic tubular network is around 6 eV. [S0163-1829(98)04504-4].://000071834900086 1098-0121ISI:000071834900086 tandings towards leading current through well-defined trajectories along an organic nanocircuit.://000257166800019 0957-4484ISI:000257166800019%315704 10.1088/0957-4484/19/31/315704 Ztagon defect in a systematical way.://000085389700004 ISI:000085389700004 d98 Elsevier Science Ltd. All rights reserved.://000074824600048 ISI:000074824600048 images is provided for a series of 27 single-wall nanotubes with diameter around 1.3 nm. (C) 2003 Wiley Periodicals, Inc.://000186143200016 ISI:00018614320001610.1002/qua.10587 rom which the geometrical orientation of the self-assembled molecules can be deduced.://000083058800019 ISI:000083058800019 electrodes cannot be used to sequence DNA by means of conductivity measurements.://000249735800020 ISI:00024973580002010.1088/0957-4484/18/42/424019 structural modeling, mechanical calculations, and experimental high-resolution transmission electron microscopy (HRTEM) data.://000228718200061 ISI:00022871820006110.1081/fst-200039482 in the fundamental absorption of water as due to exciton delocalization upon aggregation.://000244984400003 ISI:00024498440000310.1080/00268970701189186??=Vandescuren, M. Hermet, P. Meunier, V. Henrard, L. Lambin, Ph2008GTheoretical study of the vibrational edge modes in graphene nanoribbons195401-8:Physical Review B (Condensed Matter and Materials Physics)7819APS}carbon density functional theory electronic density of states localised states nanostructured materials phonons Raman spectra-http://link.aps.org/abstract/PRB/v78/e195401 ign novel functional materials for specific electronic and optoelectronic applications. (c) 2007 Wiley Periodicals, Inc.://000248979000008 ISI:00024897900000810.1002/qua.21411PKVe9I/**refs.FRM 0B< !// !HPRIMARYyearIndex 6ByP/) idreference_type text_stylesauthoryear title pages secondary_title volume numbernumber_of_volumessecondary_authorplace_published publishersubsidiary_authoredition keywords type_of_workdate2)  abstractlabelurltertiary_titletertiary_author notes isbn custom_1 custom_2 custom_3 custom_4alternate_titleaccession_number call_number short_title custom_5 custom_6sectionoriginal_publicationH) reprint_editionreviewed_itemauthor_addressimagecaption custom_7 electronic_resource_number link_to_pdf translated_author translated_titlename_of_databasedatabase_providerresearch_notes language access_datelast_modified_date !! H!H!H! (H! 3H! >H! IH! TH!_H!jH!uH! H!H!H! H! H!H! H!H!H!H!H! H! H! H! H! %H! 0H!;H!FH! QH! \H! gH! rH!}H!H!H!H!H!H!H! H! H! H! H! H!H! H!H! 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