The puzzling stability of monatomic gold wires

We have examined theoretically the spontaneous thinning process of tip-susp ended nanowires, and subsequently studied the structure and stability of th e monatomic gold wires recently observed by transmission electron microscop y. The methods used include thermodynamics, classical many-body force simul ations, local density and generalized gradient electronic structure calcula tions as well as ab initio simulations including the two tips. The wire thi nning is well explained in terms of a thermodynamic tip suction driving mig ration of surface atoms from the wire to the tips. For the same reason the monatomic wire becomes progressively stretched. Surprisingly, however, all calculations so far indicate that the stretched monatomic gold wire should be unstable against breaking, contrary to the apparent experimental stabili ty. The possible reasons for this stability are discussed. (C) 1999 Elsevie r Science B.V. All rights reserved.