The effects of steps, coupling to substrate vibrations, and surface coverage on surface diffusion rates and kinetic isotope effects: Hydrogen diffusion on Ni

We have applied canonical variational transition state theory with semiclassical transmission coefficients to investigate the dynamical effects of metal motions, surface defects (namely, steps), and surface coverage on the diffusion of H on the Ni(100) surface. We have used the embedded diatomics-in-molecules (EDIM) method to represent the hydrogen–hydrogen, hydrogen–metal, and metal–metal interactions. The roles of metal motions, surface defects, and coverage in the overall diffusion rates and kinetic isotope effects are discussed in detail, and comparisons with experimental data are made.