Correlating Force-Conductance-Structure in Au-1,8-Octanedithiol-Au Molecular Electronics

Because atomic-scale junction configurations cannot be directly resolved during break-junction measurements, simulations are needed to connect experimental force and conductance signatures with plausible interfacial structures. Here, we use configurational-bias Monte Carlo, driven molecular dynamics, and DFT+NEGF transport calculations to interpret the electromechanical response of Au-1,8-octanedithiol (ODT)-Au junctions measured by conductive atomic force microscopy break-junction experiments. Under cyclic stretching and compression with a modulation amplitude of 1.2 Å, reproducible force and conductance responses are observed. The simulations generate metastable configurations containing one, two, and three bridging ODT molecules and reproduce characteristic force ranges and conductance levels consistent with experiment. Structural analysis reveals configuration-dependent load distribution, junction deformation, molecular reorientation, and local Au-S coordination. The DFT+NEGF results further show that conductance modulation is governed mainly by changes in the Au-S contacts rather than deformation of the alkane backbone. These findings provide an atomistic interpretation of the measured electromechanical responses and clarify how junction configuration and contact rearrangement influence transport in Au-ODT-Au molecular junctions.