H/Pd(111) Absorption and Desorption Dynamics -Hydrogen-Induced Lattice Relaxation Effects-

We investigate the effects of hydrogen-induced surface lattice relaxation on the dynamics of hydrogen absorption into the surface and desorption from the subsurface to the Pd(111) surface. We perform quantum dynamics calculations with and without surface lattice motion. From the results of both hydrogen absorption and desorption probability, we can see that the hydrogen motion and the surface lattice relaxation are dynamically coupled and, depending on the initial conditions, the surface lattice motion either promotes or hinders the penetration of hydrogen into (desorption from) the surface (subsurface). We observe tunneling of hydrogen through the energy barrier hindering the hydrogen from penetration into (desorption from) the surface (subsurface). We also investigate the surface temperature dependence of hydrogen absorption dynamics. From the results, we can see that the absorption probability increases (decreases) as the surface temperature increases in the low (high) hydrogen's initial translational energy regions.