  Spin-density-functional calculations of tip-suspended gold chains, with
molecular oxygen, or dissociated oxygen atoms, incorporated in them, reveal
structural transitions for varying lengths. The nanowires exhibit enhanced
strength for both oxygen incorporation modes, and upon stretching tip atoms
join the wire. With incorporated molecular oxygen the wire conductance is about
1(2e2/h), transforming to an insulating state beyond a critical length. The
nanowire conductance with embedded oxygen atoms is low, 0.2 (2e2/h), and it
develops magnetic moments localized on the oxygens and the neighboring Au
atoms.
