@article{hernandez_meunier_smith_rurali_terrones_nardelli_terrones_luzzi_charlier_2003, title={Fullerene coalescence in nanopeapods: A path to novel tubular carbon}, volume={3}, ISSN={["1530-6992"]}, DOI={10.1021/nl034283f}, abstractNote={A 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.}, number={8}, journal={NANO LETTERS}, author={Hernandez, E and Meunier, V and Smith, BW and Rurali, R and Terrones, H and Nardelli, MB and Terrones, M and Luzzi, DE and Charlier, JC}, year={2003}, month={Aug}, pages={1037–1042} }
 @article{nakhmanson_calzolari_meunier_bernholc_nardelli_2003, title={Spontaneous polarization and piezoelectricity in boron nitride nanotubes}, volume={67}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.67.235406}, abstractNote={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. order of magnitude weaker than those of PZT. 3 In this paper, we examine spontaneous polarization and piezoelectricity in boron nitride nanotubes ~BNNT's! in order to estimate their potential usefulness in various pyroelectric and piezoelectric device applications, and to understand the interplay between symmetry and polarization in nanotubular systems. BNNT's, broadly investigated since their initial predic- tion 4 and succeeding discovery, 5 are already well known for their excellent mechanical properties. 6 However, unlike car- bon nanotubes ~CNT's !, most of BN structures are noncen- trosymmetric and polar, which might suggest the existence of nonzero spontaneous polarization fields. Recently, these properties have been partially explored by Mele and Kral, using a model electronic Hamiltonian. 7 They predicted that BNNT's are piezoelectric and pyroelectric, with the direction of the spontaneous electric field that changes with the index of the tubes. The ab initio calculations presented in this pa- per provide a much fuller description and show that BNNT systems are indeed excellent lightweight piezoelectrics, with comparable or better piezoelectric response and superior me- chanical properties than in piezoelectric polymers. However, contrary to the conclusions of Ref. 7, our combined Berry phase and Wannier function ~WF! analysis demonstrates that electronic polarization in BNNT's does not change its direc- tion but rather grows monotonically with the increasing di- ameter of the tube. Furthermore, the electronic and ionic spontaneous polarizations in BNNT's cancel exactly and these systems are pyroelectric only if their intrinsic helical symmetry is broken by, e.g., intertube interactions or elastic distortions. The rest of this paper is organized as follows: Sec. II briefly reviews the formulation of the modern polarization theory in terms of Berry phases or Wannier functions. It also presents the details of the numerical techniques that were used to compute polarization. In Sec. III we discuss the re- sults and the complementary nature of the two techniques to compute the spontaneous polarization. Finally, Sec. IV pre- sents the summary and conclusions.}, number={23}, journal={PHYSICAL REVIEW B}, author={Nakhmanson, SM and Calzolari, A and Meunier, V and Bernholc, J and Nardelli, MB}, year={2003}, month={Jun} }
 @article{meunier_kephart_roland_bernholc_2002, title={Ab initio investigations of lithium diffusion in carbon nanotube systems}, volume={88}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.88.075506}, abstractNote={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.}, number={7}, journal={PHYSICAL REVIEW LETTERS}, author={Meunier, V and Kephart, J and Roland, C and Bernholc, J}, year={2002}, month={Feb} }
 @article{roland_meunier_larade_guo_2002, title={Charge transport through small silicon clusters}, volume={66}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.66.035332}, abstractNote={With 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.}, number={3}, journal={PHYSICAL REVIEW B}, author={Roland, C and Meunier, V and Larade, B and Guo, H}, year={2002}, month={Jul} }
 @article{meunier_roland_bernholc_nardelli_2002, title={Electronic and field emission properties of boron nitride/carbon nanotube superlattices}, volume={81}, ISSN={["1077-3118"]}, DOI={10.1063/1.1491013}, abstractNote={BN/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.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Meunier, V and Roland, C and Bernholc, J and Nardelli, MB}, year={2002}, month={Jul}, pages={46–48} }
 @misc{bernholc_brenner_nardelli_meunier_roland_2002, title={Mechanical and electrical properties of nanotubes}, volume={32}, ISSN={["1531-7331"]}, DOI={10.1146/annurev.matsci.32.112601.134925}, abstractNote={▪ Abstract  We 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.}, number={2002}, journal={ANNUAL REVIEW OF MATERIALS RESEARCH}, author={Bernholc, J and Brenner, D and Nardelli, MB and Meunier, V and Roland, C}, year={2002}, pages={347-+} }
 @article{simonis_goffaux_thiry_biro_lambin_meunier_2002, title={STM study of a grain boundary in graphite}, volume={511}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(02)01511-X}, abstractNote={A 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.}, number={1-3}, journal={SURFACE SCIENCE}, author={Simonis, P and Goffaux, C and Thiry, PA and Biro, LP and Lambin, P and Meunier, V}, year={2002}, month={Jun}, pages={319–322} }
 @article{oh_meunier_ham_nemanich_2002, title={Single electron tunneling of nanoscale TiSi2 islands on Si}, volume={92}, ISSN={["0021-8979"]}, DOI={10.1063/1.1499531}, abstractNote={Nanoscale 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 °C). The lateral diameter of typical islands are ∼5 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.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Oh, J and Meunier, V and Ham, H and Nemanich, RJ}, year={2002}, month={Sep}, pages={3332–3337} }
 @article{meunier_nardelli_roland_bernholc_2001, title={Structural and electronic properties of carbon nanotube tapers}, volume={64}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.64.195419}, abstractNote={Since their initial discovery in 1990 by Iijima, 1 carbon nanotubes have come under ever increasing scientific scrutiny. They not only have outstanding mechanical and electrical properties, but also show considerable technological potential as field emitters and electrochemical storage devices. 2 In the emerging field of nanotechnology, carbon nanotubes are playing a crucial role by providing a suitable ‘‘test bed’’ or ‘‘laboratory’’ for materials properties at the nanometer length scale. Single-wall carbon nanotubes are formed when a graphene sheet is curled up into a cylinder and the carbon atoms are joined seamlessly to each other. Nanotubes are therefore characterized by their length, diameter, and helicity. The latter is a measure of the orientation of the graphene sheet as it is folded to form nanotubes. Following the notation of Hamada et al., 3 the structure of a nanotube is described by a pair of integers ( l,m), which give the coordinates of its circumference vector in the basis of the primitive lattice vector of graphene. The helicity is important because it determines both the mechanical and electrical properties of}, number={19}, journal={PHYSICAL REVIEW B}, author={Meunier, V and Nardelli, MB and Roland, C and Bernholc, J}, year={2001}, month={Nov} }
 @article{lambin_meunier_rubio_2000, title={Electronic structure of polychiral carbon nanotubes}, volume={62}, number={8}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Lambin, P. and Meunier, V. and Rubio, A.}, year={2000}, pages={5129–5135} }
 @article{meunier_lambin_2000, title={Scanning tunneling microscopy and spectroscopy of topological defects in carbon nanotubes}, volume={38}, ISSN={["1873-3891"]}, DOI={10.1016/S0008-6223(99)00296-1}, abstractNote={Scanning 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.}, number={11-12}, journal={CARBON}, author={Meunier, V and Lambin, P}, year={2000}, pages={1729–1733} }