During the fracture of nanocontacts gold spontaneously forms freely suspended chains of atoms, which is not observed for the isoelectronic noble metals Ag and Cu. Au also differs from Ag and Cu in forming reconstructions at its low-index surfaces. Using mechanically controllable break junctions we show that all the $5d$ metals that show similar reconstructions (Ir, Pt, and Au) also form chains of atoms, while both properties are absent in the $4d$ neighbor elements (Rh, Pd, and Ag), indicating a common origin for these two phenomena. A competition between $s$ and $d$ bonding is proposed as an explanation.

• Received 3 July 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.266102