  The unusual structural stability of gold nanowires at large separations of
gold atoms is explained from first-principles quantum mechanical calculations.
We show that undetected light atoms, in particular hydrogen, stabilize the
experimentally observed structures, which would be unstable in pure gold wires.
The enhanced cohesion is due to the partial charge transfer from gold to the
light atoms. This finding should resolve a long-standing controversy between
theoretical predictions and experimental observations.
