Simple approach to current-induced bond weakening in ballistic conductors

We present a simple, first-principles scheme for calculating mechanical properties of nonequilibrium bulk systems assuming an ideal ballistic distribution function for the electronic states described by the external voltage bias. This allows for fast calculations of estimates of the current-induced stresses inside bulk systems carrying a ballistic current. The stress is calculated using the Hellmann-Feynman theorem, and is in agreement with the derivative of the nonequilibrium free energy. We illustrate the theory and present results for one-dimensional (1D) metal chains of Au, Cu, Al, Pt, Pb, and Ir. We compare the dependence of ultimate tensile strength on the applied voltage which shows a remarkable difference. In particular, for these model systems, gold is seen to be the most stable under strong current, while aluminum is the least stable. Interestingly, this agrees with the ordering of break voltages among the metals found in experiments, suggesting that a current-induced "embrittlement"effect could play a role.