Transient Deformation Regime in Bending of Single-Walled Carbon Nanotubes

Pure bending of single-walled carbon nanotubes between (5,5) and (50,50) is studied using molecular dynamics based on the reactive bond order potential. Unlike smaller nanotubes, bending of (15,15) and larger ones exhibits an intermediate deformation in the transition between the buckled and fully kinked configurations. This transient bending regime is characterized by a gradual and controllable flattening of the nanotube cross section at the buckling site. Unbending of a kinked nanotube bypasses the transient bending regime, exhibiting a hysteresis due to van der Waals attraction between the tube walls at the kinked site

Analytical carbon-oxygen reactive potential

We present a reactive empirical potential with environment-dependent bond strengths for the carbon-oxygen (CO) system. The distinct feature of the potential is the use of three adjustable parameters characterizing the bond: the strength, length, and force constant, rather than a single bond order parameter, as often employed in these types of potentials. The values of the parameters are calculated by fitting results obtained from density functional theory. The potential is tested in a simulation of oxidative unzipping of graphene sheets and carbon nanotubes. Previous higher-level theoretical predictions of graphene unzipping by adsorbed oxygen atoms are confirmed. Moreover, nanotubes with externally placed oxygen atoms are found to unzip much faster than flat graphene sheets

Contact angles, ordering, and solidification of liquid mercury in carbon nanotube cavities

Optimized model potentials for mercury-mercury and mercury-carbon interactions are used in molecular dynamics simulations to study wetting and solidification of liquid mercury encapsulated in single-walled carbon nanotubes. The contact angle of mercury in the nanotube cavity increases linearly with wall curvature. The solid-liquid transition becomes less well defined as nanotube diameter decreases, while the melting temperature drops exponentially. A concentric cylindrical-shell structure is predicted for solidified mercury in small (20,20) nanotubes, while a polycrystalline structure appears in larger (40,40) nanotubes

Electrowetting in Carbon Nanotubes

We demonstrate reversible wetting and filling of open single-wall carbon nanotubes with mercury by means of electrocapillary pressure originating from the application of a potential across an individual nanotube in contact with a mercury drop. Wetting improves the conductance in both metallic and semiconducting nanotube probes by decreasing contact resistance and forming a mercury nanowire inside the nanotube. Molecular dynamics simulations corroborate the electrocapillarity-driven filling process and provide estimates for the imbibition speed and electrocapillary pressure

Influence of band width on the scattered ion yield spectra of a He + Ion by resonant or quasi-resonant charge exchange neutralization

The influence of the band structure, especially the bandwidth, on the scattered ion yield spectra of a He+ ion by the resonant or quasi-resonant neutralization was theoretically examined using quantum rate equations. When calculating the scattered ion yield spectra of He+ to simulate the experimental data, we observed that the band structure, especially the bandwidth, had a strong influence on the spectra at relatively low incident He+ ion energies of less than several hundred eV. Through many simulations, it was determined that theoretical calculations that include bandwidth calculation can simulate or reproduce the experimentally observed spectra of He+-In, He+-Ga, and He+-Sn systems. In contrast, simulations not including bandwidth simulation could neither reproduce nor account for such spectra. Furthermore, the calculated ion survival probability (ISP) at low incident ion energies tended to decrease with increasing bandwidth. This decrease in ISP probably corresponds to the relatively small scattered ion yield usually observed at low incident ion energies. Theoretically, such a decrease indicates that a He+ ion with a low incident energy can be easily neutralized on the surface when the bandwidth is large