6 DIMENSIONAL QUANTUM DYNAMICS STUDY FOR DISSOCIATIVE ADSORPTION OF H-2 ON CU(111) SURFACE

In this letter we present preliminary results of full six dimensional quantum dynamics calculations for dissociative adsorption of a hydroge n molecule on a Cu(111) surface. We utilize the time-dependent wave-pa cket approach to simulate the dissociation process on a full dimension al LEPS potential energy surface which has incorporated the latest ab initio data [Hammer et al. Phys. Rev. Lett. 73, 1400 (1994)]. We use a novel partitioning of the angular momentum operator In the split-oper ator method so that a direct product DVR can be rigorously implemented . The most interesting, observation in the present rigorous quantum dy namics study is the site-averaged effect, i.e., the averaged dissociat ion probability of the four dimensional calculations over the three sy mmetric impact sites strongly resembles the exact dissociation probabi lity of the six dimensional calculations. In accord with the low dimen sional calculations, initial vibrational excitation of H-2 effectively reduces the translational threshold energy. The rotational orientatio n effect observed in the four dimensional studies remains in the prese nt full dimensional dynamics with the cartwheel orientation yielding d ramatically lower dissociative efficiency than the energetically equiv alent helicopter orientation. We focus on normal incident scattering. The diffractive scattering and more detailed results will be presented in a later paper. (C) 1997 American Institute of Physics.