Nanomechanical Properties and Phase Transitions in a Double-Walled (5,5)@(10,10) Carbon Nanotube: ab initio Calculations

The structure and elastic properties of (5,5) and (10,10) nanotubes, as well as barriers for relative rotation of the walls and their relative sliding along the axis in a double-walled (5,5)@(10,10) carbon nanotube, are calculated using the density functional method. The results of these calculations are the basis for estimating the following physical quantities: shear strengths and diffusion coefficients for relative sliding along the axis and rotation of the walls, as well as frequencies of relative rotational and translational oscillations of the walls. The commensurability-incommensurability phase transition is analyzed. The length of the incommensurability defect is estimated on the basis of ab initio calculations. It is proposed that (5,5)@(10,10) double-walled carbon nanotube be used as a plain bearing. The possibility of experimental verification of the results is discussed.Comment: 14 page

Quantifying the Stacking Registry Matching in Layered Materials

A detailed account of a recently developed method [Marom et al., Phys. Rev. Lett. 105, 046801 (2010)] to quantify the registry mismatch in layered materials is presented. The registry index, which was originally defined for planar hexagonal boron-nitride, is extended to treat graphitic systems and generalized to describe multi-layered nanotubes. It is shown that using simple geometric considerations it is possible to capture the complex physical features of interlayer sliding in layered materials. The intuitive nature of the presented model and the efficiency of the related computations suggest that the method can be used as a powerful characterization tool for interlayer interactions in complex layered systems.Comment: 8 pages, 8 figures. To be published in a special issue of the Israel Journal of Chemistry regarding "Inorganic Nanotubes and Nanostructures

Controls on explosive-effusive volcanic eruption styles

One of the biggest challenges in volcanic hazard assessment is to understand how and why eruptive style changes within the same eruptive period or even from one eruption to the next at a given volcano. This review evaluates the competing processes that lead to explosive and effusive eruptions of silicic magmas. Eruptive style depends on a set of feedbacks involving interrelated magmatic properties and processes. Foremost of these are magma viscosity, gas loss, and external properties such as conduit geometry. Ultimately, these parameters control the speed at which magmas ascend, decompress and outgas en route to the surface, and thus determine eruptive style and evolution

Impact-induced changes in source depth and volume of magmatism on Mercury and their observational signatures

Mantle partial melting produced the volcanic crust of Mercury. Here, the authors numerically model the formation of post-impact melt sheets and find that mantle convection was weak at around 3.7–3.8 Ga and that the melt sheets of Caloris and Rembrandt may contain partial melting of pristine mantle material

Low-energy electron transmission in a partially unzipped zigzag nanotube

Based on the nearest-neighbor tight-binding approximation, we present exact analytical expressions for electron transmission in nanotube/ribbon junctions, generated by incomplete unzipping of zigzag nanotubes. By assuming one-dimer-line difference in the widths of the leads, it is demonstrated that such a contact exhibits zero backscattering of low-energy electrons entering from the graphene side of the junction. We also show that a zigzag nanotube section sandwiched between two armchair graphene ribbons is completely transparent for incident low-energy electrons. Possible application of the results to nanosensor engineering is also included. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010