Carbon-based nanotechnology on a supercomputer

The quantum nature of phenomena dominating the behaviour of nanostructures raises new challenges when trying to predict and understand the physical behaviour of these systems. Addressing this challenge is imperative in view of the continuous reduction of device sizes, which is rapidly approaching the atomic level. Since even the most advanced experimental observations are subject to being fundamentally influenced by the measurement itself, new approaches must be sought to design and test future building blocks of nanotechnology. In this respect, high-performance computing, allowing predictive large-scale computer simulations, has emerged as an indispensable tool to foresee and interpret the physical behaviour of nanostructures, thus guiding and complementing the experiment. This contribution will review some of the more intriguing phenomena associated with nanostructured carbon, including fullerenes, nanotubes and diamondoids. Due to the stability of the sp2 bond, carbon fullerenes and nanotubes are thermally and mechanically extremely stable and chemically inert. They contract rather than expand at high temperatures, and are unparalleled thermal conductors. Nanotubes may turn into ballistic electron conductors or semiconductors, and even acquire a permanent magnetic moment. In nanostructures that form during a hierarchical self-assembly process, even defects may play a different, often helpful role. sp2 bonded nanostructures may change their shape globally by a sequence of bond rotations, which turn out to be intriguing multi-step processes. At elevated temperatures, and following photo-excitations, efficient self-healing processes may repair defects, thus answering an important concern in molecular electronics. (topical review)