Surface chemistry in three dimensions: CO dissociation between two surfaces

Based on self-consistent density functional calculations it is shown that a new dissociation process for CO adsorbed on a Ru(0001) surface is made pos sible when the distance to a second Ru(0001) surface placed just above it i s below some critical value. This '3D' process is more facile than the usua l single surface ('2D') process because indirect adsorbate-adsorbate intera ctions in the transition state are absent in the '3D' case. The prospects f or STM-induced single molecule chemistry and for '3D' catalysts are discuss ed. (C) 2000 Elsevier Science B.V. All rights reserved.