Extensive LDA and quasi-particle calculations have been performed on boron nitride (BN) single-wall multi-wall nanotubes. Strain energies are found to be smaller for BN nanotubes than carbon of the same radius, owing a buckling effect which stabilizes tubular structure. For tubes larger 9.5 Å in diameter, lowest conduction band is predicted free-electron-like with electronic charge density localized inside tube. these tubes, this at constant energy above top valence band. Consequently,...

This article reviews the electronic and transport properties of carbon nanotubes. The focus is mainly theoretical, but when appropriate relation with experimental results mentioned. While simple band-folding arguments will be invoked to rationalize how metallic or semiconducting character nanotubes inferred from their topological structure, more sophisticated tight-binding ab initio treatments introduced discuss subtle physical effects, such as those induced by curvature, tube-tube...

The quasiparticle band structure of bulk hexagonal boron nitride is studied within the GW approximation for self-energy operator. influence interlayer distance on investigated both local density and approach, importance an state in determining gap demonstrated. Also, isolated sheet calculated. We show that equivalent case plays same role as determing gap.

We report on a numerical study of electronic transport in chemically doped 2D graphene materials. By using ab initio calculations, self-consistent scattering potential is derived for boron and nitrogen substitutions, fully quantum-mechanical Kubo-Greenwood approach used to evaluate the resulting charge mobilities conductivities systems with impurity concentration ranging within [0.5, 4.0]%. Even doping as large 4.0%, conduction marginally affected by quantum interference effects, preserving...

We report the successful synthesis of ${\mathrm{B}}_{\mathit{x}}$${\mathrm{C}}_{\mathit{y}}$${\mathrm{N}}_{\mathit{z}}$ nanotubes. Arc-discharge methods were used to produce stable nanotubule structures identified by high-resolution transmission-electron microscopy. Local electron-energy-loss spectroscopy K-edge absorptions for B, C, and N atoms was determine atomic compositions individual tubules. Tubes stoichiometry ${\mathrm{BC}}_{2}$N ${\mathrm{BC}}_{3}$ have been observed, in agreement...

We evaluate the performances of ab initio GW calculations for ionization energies and HOMO-LUMO gaps thirteen gas phase molecules interest organic electronic photovoltaic applications, including C60 fullerene, pentacene, free-base porphyrins phtalocyanine, PTCDA, standard monomers such as thiophene, fluorene, benzothiazole or thiadiazole. Standard G0W0 calculations, that is starting from eigenstates obtained with local semilocal functionals, significantly improve energy band gap compared to...

Quasiparticle band structures of six II-VI compounds (ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe in the zinc-blende wurtzite structures) are calculated using GW approximation. Results for structures, ab initio pseudopotential method within local-density approximation (LDA), given along with energies quasiparticle excitations at symmetry points. Comparisons made measured values trends corrections to LDA examined.

We present first-principles calculations of quantum transport in chemically doped graphene nanoribbons with a width up to 4 nm. The presence boron and nitrogen impurities is shown yield resonant backscattering, whose features are strongly dependent on the symmetry ribbon, as well position dopants. Full suppression backscattering obtained $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}$ plateau when impurity preserves mirror armchair ribbons. Further, an unusual acceptor-donor...

The 0–0 energies of 80 medium and large molecules have been computed with a panel theoretical formalisms. We used an approach computationally tractable for molecules, that is, the structural vibrational parameters are obtained TD-DFT, solvent effects accounted PCM model, whereas total transition determined TD-DFT five wave function approaches accounting contributions from double excitations, namely, CIS(D), ADC(2), CC2, SCS-CC2, SOS-CC2, as well Green's based BSE/GW approach. Atomic basis...

We perform benchmark calculations of the Bethe–Salpeter vertical excitation energies for set 28 molecules constituting well-known Thiel's set, complemented by a series small representative dye chemistry field. show that based on molecular orbital energy spectrum obtained with non-self-consistent G0W0 starting from semilocal DFT functionals dramatically underestimate transition energies. Starting popular PBE0 hybrid functional significantly improves results even though this leads to an...

The Bethe–Salpeter equation (BSE) formalism is steadily asserting itself as a new efficient and accurate tool in the ensemble of computational methods available to chemists order predict optical excitations molecular systems. In particular, combination so-called GW approximation, giving access reliable ionization energies electron affinities, BSE formalism, able model UV/vis spectra, has shown provide singlet excitation with typical error 0.1–0.3 eV. With similar cost time-dependent...

The stability and electronic properties of composite BxCyNznanotube heterojunctions were studied using both ab initio semi-empirical approaches. C/BN BC2N/BN superlattices or isolated junctions investigated as specific examples the wide variety devices that can be realized such nanotubes. characteristics these are predicted to largely independent radius, helicity, multiplicity, degree perfection constituting

The uncatalyzed edge growth of carbon nanotubes was investigated by first-principles molecular dynamics simulations. At experimental temperatures the open end single-walled closed spontaneously into a graphitic dome, which may explain why these do not grow in absence transition metal catalysts. On other hand, chemical bonding between edges adjacent coaxial tubes (“lip-lip” interactions) trapped double-walled nanotube metastable energy minimum, thus preventing dome closure. These calculations...

Ab initio photoabsorption cross sections of small silicon and alkali clusters (Li, Na) have been calculated by a new method. Different structural isomers given cluster give rise to clearly distinguishable spectra. Inclusion screening effects is shown be essential describe the We propose that comparison theoretical spectra with measured ones would serve as useful tool discern structure semiconductor clusters. Low temperature measurements and/or line-shape analysis are needed extract detailed...

We present an ab initio study of the recently discovered superconductivity boron doped diamond within framework a phonon-mediated pairing mechanism. The role dopant, in substitutional position, is unconventional that half coupling parameter $\ensuremath{\lambda}$ originates strongly localized defect-related vibrational modes, yielding very peaked Eliashberg ${\ensuremath{\alpha}}^{2}F(\ensuremath{\omega})$ function. electron-phonon potential found to be extremely large, and ${T}_{C}$ limited...

We study within the perturbative many-body $GW$ and Bethe-Salpeter approach low lying singlet charge-transfer excitations in molecular donor-acceptor complexes associating benzene, naphtalene anthracene derivatives with tetracyanoethylene acceptor. Our calculations demonstrate that such techniques can reproduce experimental data a mean average error of 0.1-0.15 eV for present set dimers, excellent agreement best time-dependent density functional studies optimized range-separated functionals....

On the basis of first-principles GW calculations, we study quasiparticle properties guanine, adenine, cytosine, thymine, and uracil DNA RNA nucleobases. Beyond standard ${G}_{0}{W}_{0}$ starting from Kohn-Sham eigenstates obtained with (semi)local functionals, a simple self-consistency on eigenvalues allows us to obtain vertical ionization energies electron affinities within an average 0.11 0.18 eV error, respectively, as compared state-of-the-art coupled-cluster multiconfigurational...

We discuss a model for the onsite matrix elements of $s{p}^{3}{d}^{5}{s}^{\ensuremath{\ast}}$ tight-binding Hamiltonian strained diamond or zinc-blende crystal nanostructure. This features onsite, off-diagonal couplings among $s$, $p$, and $d$ orbitals is able to reproduce effects arbitrary strains on band energies effective masses in full Brillouin zone. It introduces only few additional parameters free from any ambiguities that might arise definition macroscopic as function atomic...

We present in this review a joint experimental and theoretical overview of the synthesis techniques properties boron-nitride (BN) boron-carbonitride (BCN) nanotubes. While their tubular structure is similar to that carbon analogues, we show electronic are significantly different. BN tubes wide band gap insulators while BCN systems can be semiconductors with visible range.

We study the electronic and optical properties of 39 small molecules containing transition metal atoms 7 others related to quantum-dots for photovoltaics. explore in particular merits many-body GW formalism, as compared ΔSCF approach within density functional theory, description ionization energy affinity. Mean average errors 0.2–0.3 eV with respect experiment are found when using PBE0 a starting point GW. The effect partial self-consistency at level is explored. Further, excitations,...