Current-voltage curves for molecular junctions: Metal basis set vs. cluster size

A 21 Au atom description of the contacts supports previous work that used only six Au atoms. Using the LANL1 (3s3p3d)/[1s1p1d] Au basis set in conjunction with the six atom cluster leads to solutions with excess charge on the Au atoms. While using the (3s3p3d)/[1s1p1d] Au basis set for all atoms in a larger 21 Au atom cluster also yields a non-physical solution, it is possible to use the full minimal basis set on the Au atoms that are not at the edge of the cluster.