Hydrogen Welding and Hydrogen Switches in a Monatomic Gold Nanowire

Ab initio density-functional calculations are performed to study the interaction between a monatomic gold nanowire suspended between two
gold tips and hydrogen, in the molecular, quasi-dissociated, dissociated, and atomic forms. Structural configurations, electronic states, vibrational
modes, and electronic transport are investigated for several elongation stages of the wire, corresponding to the last conductance plateau (G
≈ 1 g0, g0 ) 2e2/h) before breaking of the contact. We illustrate “welding” and restoration of electric conductance of a broken wire through
the incorporation of an H2 molecule, and an electric switching action resulting from structural fluctuations of an adsorbed molecule caused
by mechanical forces applied to the wire.