Potential Energy Hypersurfaces for the Interaction of NO with the Ag (111)Surface

摘要

We present a new potential energy surface for the interaction of the NO moleculewith a close-packed A g (1 1 1) surface obtained using the recently developed corrected effective medium (CEM) method. The dual NO-Ag(1 1 1) interaction potentials, which reflect the electronic orbital degeneracy of the NO molecule in its ground (X2II) electronic state, were determined at a large variety of distances and orientations of the NO molecule above the surface, and for approach of the molecule over three different sites on the surface unit cell, described by a cluster of greater than 10 Ag atoms. The more than 600 calculated interaction energies were then fit to a compact analytic form, which allows the determination of the interaction potential at any position above the surface. The strongest binding corresponds to a nearly flat orientation of the NO molecule, with approach of the N end slightly preferred, and with the single antibonding orbital of NO pointing toward the surface. In this geometry, the binding energy above, respectively, the atop, two-fold bridge, and three-fold center sites site is 2200, 1773, and 1574 cm-1. By contrast when the antibonding electron is oriented in a plane parallel to the surface, the binding energy diminishes dramatically, and the dependence of the interaction energy on the orientation of the NO molecule is also diminished. Here, the three-fold center site is preferred, but