Nanotubules of bare boron clusters: Ab initio and density functional study

Using ab initio quantum-chemical and density functional methods we have determined novel structures of bare boron clusters. In addition to previously reported quasi-planar, convex and spherical cluster forms, boron nanotubules seem to be highly stable as well. These novel nanotubular structures are composed of hexagonal pyramids only and can be considered as segments of extended pipes. Applying a previously reported "Aufbau Principle", one can easily construct stable boron structures besides the new nanotubular clusters described below. Thus the Aufbau principle should help in illuminating the chemical and physical nature of new boron materials based on boron nanotubules.