By ab initio simulation in the density-functional–local-density approximation, we study the structural and electronic properties of a monolayer of Pd-porphyrin and perylene on a Au(111) slab, and we investigate the response of this interface to an external electrostatic field. Our computation closely mimics the metal/organic junction investigated experimentally by Fischer et al. [Europhys. Lett. 28, 129 (1994)] that has been shown to display rectifying behavior and charging effects associated with molecular conduction via single-electron tunneling. The ab initio model allows us to determine the conditions for molecular tunneling and to investigate their dependence on structural and chemical parameters. Moreover, it provides a direct view of screening at the molecular level. © 1996 The American Physical Society.

• Received 12 February 1996

DOI:https://doi.org/10.1103/PhysRevB.54.5097