Molecular alligator clips for single molecule electronics. Studies of group 16 and isonitriles interfaced with Au contacts

A density-functional-theory treatment has been carried out on chalcogenide- and isonitrile-containing molecular systems (alligator clips) involved at the interface of molecule/Au-electrode contacts. The B3PW91 functional was used with effective core potentials provided within the LANL2DZ potentials and basis set. An extended basis set, LANL-E, was implemented by combining the valence, diffuse, and polarization basis from the 6-311++G** for H, C, N, S, and Se and by adding polarization and diffuse functions for Te and Au atoms. Results, including bond lengths and angles, ionization potentials, electron affinities, and binding energies for small systems containing Au atoms, were obtained with acceptable precision for those systems with available experimental information. Predicted quantities are reported for other systems that, as yet, have no experimental information available. This study indicates that, of the alligator clips studied, S would provide the best embodiment followed closely by Se- and Te-terminated molecules. This study also indicates that the precision obtained with calculations of first- and second-row atom-containing molecules can also be achieved with systems possessing heavier elements such as Au.