DISSOCIATIVE ADSORPTION OF O-2 ON CU(110) AND CU(100) - 3-DIMENSIONALQUANTUM DYNAMICS STUDIES

The dynamics of dissociative chemisorption of oxygen on Cu(110) and Cu (100) has been studied using a time-dependent quantum wave-packet appr oach. Dissociation probabilities for O-2 on both (110) and (100) surfa ces of copper are calculated for ground state as well as rovibrational ly excited oxygen molecules. The present calculation simulates O-2 dis sociation on nascent copper surfaces with no consideration for surface reconstruction. The dynamics calculation is based on a flat-surface m odel in which three molecular degrees of freedom are explicitly includ ed while the lateral coordinates of the molecule are neglected. The in teraction potential energy surface (PES) for the dynamics calculation is constructed using the LEPS (London-Erying-Polyni-Sato) PES form wit h potential parameters fitted to some available experimental and theor etical data. The barrier of the LEPS PES for oxygen dissociation on co pper is 0.11 eV for Cu(110) and 0.08 eV for Cu(100). Relatively speaki ng, the saddle point of the O-2/Cu(110) PES is located near the entran ce channel, while that of the O-2/Cu(100) is near the product channel. This feature is primarily responsible for the difference in calculate d dissociation probabilities of oxygen on two surfaces. Specifically, the dissociation probability of O-2 on Cu(110) is large and less sensi tive to the vibrational excitation of the molecule, while that of O-2 on Cu(100) is much smaller and more sensitive to vibrational excitatio n of the molecule.