Molecular Device Simulations Spring Up

In molecular electronic devices, charge transport through electrode junctions can be controlled mechanically by stretching and compressing the junction components. A deeper understanding of the interplay among chemical structure, conductance, and mechanics of such junctions would therefore lead to improved electronics. Although techniques exist to study the chemistry and conductance of such systems, detailing the effects of mechanical force has proven difficult. Huachuan Wang and Yongsheng Leng of George Washington University have now developed an atomistic molecular dynamics simulation technique that incorporates mechanics by representing the elasticity of a gold electrode as a spring (J. Phys. Chem. C 2015, DOI: 10.1021/acs.jpcc.5b02843). Studying a junction involving gold electrodes linked by benzenedithiolate (BDT) molecules, the researchers found that initial pulling on the electrode leads to breaking of Au–Au contacts between the electrodes, leaving only Au–BDT–Au links. Further pulling yields two results. In the majority of cases, more Au–Au bonds break from deeper in the electrode, leading to total rupture and the junction going from high to zero conductance. In a minority of cases, an additional Au–BDT–Au bridge forms near the junction, allowing for a transition from high to low conductance before breaking entirely.