ACETYLENE ADSORPTION ON CU(111) AND STEPPED CU(111) - THEORETICAL-STUDY

ASED MO and DV-X(alpha) methods have been employed to describe the ads orption of C2H2 on the Cu(111) and stepped Cu(111) surface. Our result s show that all adsorbed C2H2 molecules are distorted because both the acetylene ir donation to the surface and substrate back-donation to t he acetylene pi() orbital result in the equilibrium bonding geometry. On the Cu(111) surface, two stable configurations are found. One is o n the bridge site with the C-C axis parallel to the surface; the other is two C atoms on the two symmetrically distinct threefold-coordinate d hollow sites on the surface. The influence and mechanism of a monato mic step with (110) geometry on the binding energy and the structure o f the adsorbate substrate complex have been investigated. The results show that two new types of chemisorption complex can be formed; the bi nding energies are largely increased.