Effect of the atomic configuration of gold electrodes on the electrical conduction of alkanedithiol molecules

The nonequilibrium Green's function approach in combination with density-functional theory was used to perform ab initio quantum-mechanical calculations of the electrical conduction of single alkanedithiol molecules sandwiched between two gold electrodes. The atomic configuration of the gold electrodes was varied in the vicinity where the molecule attaches, using configurations most likely to occur in break-junction experiments. The zero-voltage conductance is shown to depend strongly on the detailed atomic configuration of the electrodes. The transmission coefficients reveal nonresonant tunneling, which is enhanced by localized states. For certain electrode configurations, good agreement with conductance measurements [B. Q. Xu and N. J. Tao, Sci. 301, 1221 (2003)] is obtained.