ONE-DIMENSIONAL CHAINS OF METAL ATOMS

Using a first-principles, density-functional method we have studied th e electronic and structural properties of different isolated, periodic and infinite chains of Bi, Tl and Pb. In contrast to the case for cry stalline and atomic systems, these have first recently been available experimentally (e.g. as guests inside a zeolite and deposited on surfa ces). We have optimized the geometrical parameters as well as calculat ed the band structures for different structures. We find that the syst ems are very soft such that the geometry might easily be controlled or influenced by weak external perturbations, e.g. those of the zeolite walls or the surfaces. Some of the structures were found to be unstabl e without these external interactions. The band structures show that t he systems can be either metallic, semiconducting or semimetallic depe nding on their geometry and structure. It was also found that the incl usion of spin-orbit couplings was essential for a proper description o f all the properties. (C) 1997 Elsevier Science Ltd.