A pr 1 99 9 Electronic structure and dimerization of a single monatomic gold wire

The electronic structure of a single monatomic gold wire is presented for the first time. It has been obtained with state-of-the-art ab-initio full-potential density-functional (DFT) LMTO (linearized muffin-tin orbital) calculations taking into account relativistic effects. For stretched structures in the experimentally accessible range the conduction band is exactly half-filled, whereas the band structures are more complex for the optimized structure. By studying the total energy as a function of unit-cell length and of a possible bond-length alternation we find that the system can lower its total energy by letting the bond lengths alternate leading to a structure containing separated dimers with bond lengths of about 2.5 ˚ A, largely independent of the stretching. However, first for fairly large unit cells (above roughly 7 ˚ A), is the total-energy gain upon this dimerization comparable with the energy costs upon stretching. We propose that this together with band-structure effects is the reason for the larger interatomic distances observed in recent experiments. We