Влияние подложки из оксида кремния на электронные свойства и электропроводность моно- и бислойных пленок из одностенных углеродных нанотрубок типа кресло: квантово-механическое исследование

We investigate electrical properties of mono- and bilayer single-walled carbon nanotube (SWCNT) films located on silicon oxide substrates. The substrate is a silicon dioxide crystal film characterized by a P42/mnm space group with (100) surface. The single-walled carbon nanotubes are armchair nanotubes of subnanometer diameter (4,4) and nanometer diameter (7,7). It is found that the diameter of the nanotubes is of great importance and determines the electronic properties of the film on the substrate in a large degree. Thin tubes (4,4) formed in a bilayer film (with a reciprocally perpendicular orientation relative to each other) have the least resistance. The substrate has insignificant influence on the electronic properties of such a film. Films with larger diameter tubes are characterized by a higher resistance value. It is found that the important role is played by the contact surface of the SWCNT–substrate.

Pulling Simulations and Hydrogen Sorption Modelling on Carbon Nanotube Bundles

Recent progress in molecular simulation technology has developed an interest in modernizing the usual computational methods and approaches. For instance, most of the theoretical work on hydrogen adsorption on carbon nanotubes was conducted a decade ago. It should be insightful to reinvestigate the field and take advantage of code improvements and features implemented in contemporary software. One example of such features is the pulling simulation modules now available in many molecular dynamics programs. We conduct pulling simulations on pairs of carbon nanotubes and measure the inter-tube distance before they dissociate in water. We use this distance to set the interval size between adjacent nanotubes as we arrange them in bundle configurations. We consider bundles with triangular, intermediate and honeycomb patterns, and armchair nanotubes with a chiral index from n = 5 to n = 10. Then, we simulate low pressure hydrogen adsorption isotherms at 77 K, using the grand canonical Monte Carlo method. The different bundle configurations adsorb great hydrogen amounts that may exceed 2% wt at ambient pressures. The computed hydrogen capacities are considered large for physisorption on carbon nanostructures and attributed to the ultra-microporous network and extraordinary high surface area of the configured models.

Неэмпирические расчеты структуры и устойчивости нанотрубок на основе монохалькогенидов галлия

For the first time first-principles calculations were performed to get the dependences of strain energy and band gap of achiral nanotubes obtained by rolling up monolayers of gallium (II) sulfide and selenide. The hybrid density functional method (with 13% of the Hartree-Fock exchange) within the CRYSTAL17 computer code was used. The empirical Grimme correction was applied to describe the dispersion interactions between layers accurately. As a result of simulations of nanotubes with different chirality and different diameters, the minimum diameters of the stable single-walled nanotubes were determined, which retain the continuity of the chemical bonds on the outer nanotube surface. It was shown that the strain energy dependence on a diameter obeys a classical law of inverse squares and is the same for «zigzag» and «armchair» nanotubes.

Tuning the indirect–direct band gap transition in the MoS2−xSex armchair nanotube by diameter modulation

The indirect–direct band gap transition is observed in armchair nanotubes MoSSe and MoSe2 by diameter modulation.