A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.

An important issue in nanoelectromechanical systems is developing small electrically driven motors. We report on an artificial nanofabricated motor in which one short carbon nanotube moves relative to another coaxial nanotube. A cargo is attached to an ablated outer wall of a multiwalled carbon nanotube that can rotate and/or translate along the inner nanotube. The motion is actuated by imposing a thermal gradient along the nanotube, which allows for subnanometer displacements, as opposed to an electromigration or random walk effect.

We report a detailed study of the vibrational properties of BN single-walled nanotubes and of the BN monolayer. Our results have been obtained from a well-established tight-binding model complemented with an electrostatic model to account for the long-range interactions arising from the polar nature of the material and which are not included in the tight-binding model. Our study provides a wealth of data for the BN monolayer and nanotubes, such as phonon band structure, vibrational density of states, elastic constants, etc. For the nanotubes we obtain the behavior of the optically active modes as a function of the structural parameters, and we compare their frequencies with those derived from a zone-folding treatment applied to the phonon frequencies of the BN monolayer, finding general good agreement between the two.

The present work reports ab initio molecular dynamics simulations, based on density functional theory using the PBE functional, of Li⁺ - Na⁺ - and K⁺ -montmorillonites, considering three types of isomorphic substitutions in the montmorillonite layer: tetrahedral (T_sub), octahedral (O_sub) and both (OT_sub). These simulations allow us to evaluate the effect of each type of substitution on the inner- outer-sphere complex formation of the alkali cations. It is observed that, for the three kinds of substituted montmorillonites, K⁺ remains bound to the surface confirming its role as swelling inhibitor. In contrast, Li⁺ tends to hydrate and coordinate to 4 water molecules in all cases, except for OT_sub, for which one of the two Li⁺ cations remains bound to the oxygens close to the substituted tetrahedral site. Finally, Na⁺ presents an intermediate behaviour, binding to the surface in T_sub montmorillonite but being hydrated in O_sub. These simulations show that the hydration/adsorption behaviour of alkali cations in the swelling process of montmorillonite depends on the affinity of the cation for water and the surface, as well as on the type of substitution that controls the negative charge on surface oxygen atoms.