Dissociative adsorption dynamics of H2 at the atop-Pt, atop-Cu, and Cu±Pt bridge sites of an ordered Cu3Pt(1 1 1) Ð orientational effects

We present a comparative theoretical study on how orientation in¯uences H2 dissociative adsorption dynamics at different sites along the Cu3Pt(1 1 1) surface lateral direction where Cu and Pt alternate. Our total energy calculation results show nonactivated H2 dissociation at the atop-Pt site, and activated H2 dissociation at the atop-Cu and Cu±Pt bridge sites. The activation barrier for H2 dissociation across the Cu±Pt bridge site has a strong dependence on the H2 orientation with respect to the surface. Strong sensitivity of the dissociation dynamics to the orientation dependence of the reaction suggests that further information on the orientational dependence of the effective activation barrier could be obtained by comparing the orientation of the H2 before impinging on and after scattering from a surface. # 2001 Elsevier Science B.V. All rights reserved.