  We performed density functional theory and tight-binding molecular dynamics
calculations to investigate the formation of suspended linear atom chains when
stretching gold nanowires along the [110] crystal orientation. We determined
that chain formation can occur only when the crystal symmetry is broken in the
early stages of the elongation process. Such crystallographic asymmetry can be
induced by stretching the wire along a slightly off-axis tensile direction or
by introducing thermal fluctuations. Our observation of the off-axis formation
of these chains agrees with experimental findings.
