The oxygen adsorption energies for pristine and N-doped single-walled carbon nanotubes of different diameters.

We present detailed electronic band-structure calculations for antiferromagnetic chromium compounds, CuCrX(2) (X = S, Se or Te), carried out using spin-polarized density functional theory within the generalized-gradient approximation (GGA). A narrow-band semiconductor-to-metal transition is observed upon replacement of S or Se by Te. The indirect bandgap is found at 0.58 eV and 0.157 eV for CuCrS(2) and CuCrSe(2), respectively. The results for our theoretical calculations are well in line with the electronic transport properties experimentally observed for CuCrS(2) and CuCrSe(2).

We report a detailed magnetotransport study on single crystals of PrBi. The presence of felectrons in this material raises the prospect of realizing a strongly correlated version of topological semimetals. PrBi shows a magnetic field induced metal insulator transition below T ∼ 20 K and a very large magnetoresistance (≈ 4.4 × 10 4 %) at low temperatures (T = 2 K). We have also probed the Fermi surface topology by de Haas van Alphen (dHvA) and Shubnikov de Haas (SdH) quantum oscillation measurements complimented with density functional theory (DFT) calculations of the band structure and the Fermi surface. Angle dependence of the SdH oscillations have been carried out to probe the possible signature of surface Dirac fermions. We find three frequencies corresponding to one electron (α) and two hole (β and γ) pockets in experiments, consistent with DFT calculations. The angular dependence of these frequencies is not consistent with a two dimensional Fermi surface suggesting that the transport is dominated by bulk bands. Although the transport properties of this material originate from the bulk bands, the high mobility and small effective mass are comparable to other compounds in this series proposed as topologically nontrivial.

The structure of the layered transition-metal Borides AB2 (A = Os, Ru) is built up by alternating T and B layers with the B layers forming a puckered honeycomb. Here we report superconducting properties of RuB2 with a Tc ≈ 1.5 K using measurements of the magnetic susceptibility versus temperature T , magnetization M versus magnetic field H, resistivity versus T , and heat capacity versus T at various H. We observe a reduced heat capacity anomaly at Tc given by ∆C/γTc ≈ 1.1 suggesting multi-gap superconductivity. Strong support for this is obtained by the successful fitting of the electronic specific heat data to a two-gap model with gap values ∆1/kBTc ≈ 1.88 and ∆2/kBTc ≈ 1.13. Additionally, M versus H measurements reveal a behaviour consistent with Type-I superconductivity. This is confirmed by estimates of the Ginzburg-Landau parameter κ ≈ 0.1-0.66. These results strongly suggest multi-gap Type-I superconductivity in RuB2. We also calculate the band structure and obtain the Fermi surface for RuB2. The Fermi surface consists of one quasitwo-dimensional sheet and two nested ellipsoidal sheets very similar to OsB2. An additional small 4 th sheet is also found for RuB2. RuB2 could thus be the first example of a multi-gap Type-I superconductor.

We discuss the effect of the in-plane electric field on the Raman spectroscopy for few-layered MoS 2. The characteristic Raman modes of MoS 2 show gradual red shift, while the intensity increases by 45-50% as the electric field is increased, showing a large electro-optical effect. Structural analysis suggests that our few-layered MoS 2 belongs to P6/m2 space group with broken inversion symmetry. We attribute this gradual red shift to this broken symmetry-driven piezoelectricity in MoS 2 , which generates tensile strain along the perpendicular direction when the electric field is applied. The enhancement of the effect upon reversing the electric field direction adds credence to our interpretation. Our first principal density-functional theory calculation further substantiates the claim. This optical probing of the electromechanical coupling may lead to applications as a nonextensive technique for electric field/strain sensors in the nanoelectronics devices.

Basal angiosperms or Magnoliids is an important clade of commercially important plants which mainly include spices and edible fruits. In this study, 17 chloroplast genome sequences belonging to clade Magnoliids were screened for the identification of chloroplast simple sequence repeats (cpSSRs). Simple sequence repeats or microsatellites are short stretches of DNA up to 1-6 base pair in length. These repeats are ubiquitous and play important role in the development of molecular markers and to study the mapping of traits of economic, medical or ecological interest. A total of 479 SSRs were detected, showing average density of 1 SSR/6.91 kb. Depending on the repeat units, the length of SSRs ranged from 12 to 24 bp for mono-, 12 to 18 bp for di-, 12 to 26 bp for tri-, 12 to 24 bp for tetra-, 15 bp for penta- and 18 bp for hexanucleotide repeats. Mononucleotide repeats were the most frequent (207, 43.21 %) followed by tetranucleotide repeats (130, 27.13 %). Penta- and hexanucleotide repeats were least frequent or absent in these chloroplast genomes.

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The layered antiferromagnetic ACrX(2) -type compounds are currently highlighted as prominent material candidates for low- and intermediate-temperature thermoelectric (TE) applications. A key to attain the enhanced TE characteristics is to apply high-temperature sintering which presumably introduces some cation disorder. Here we present spin unrestricted density functional theory analysis of electronic band structures and TE properties of Cu and Cr disordered CuCrX(2)(X = S, Se) phases. A narrow band gap semiconductor to metal transition is observed on 8.3% Cr-site disorder for both the compounds, X = S and Se. The large p-type Seebeck coefficient realized in the metallic state for the Cr-disordered phases is the factor that makes these phases promising TE materials. These theoretical findings for the Cr-disordered phases are well in line with reported experimental data for electronic transport properties. Contrarily, the results revealed for the Cu-disordered phases do not agree with the experimental data. Hence the results of our theoretical analysis strongly point towards the Cr rather than the Cu disorder picture to explain the TE electronic transport characteristics of the high-temperature sintered phases of CuCrX(2)(X = S, Se).