[on surface thermodynamics and kinetics]
“If we want a faithful and not oversimplified picture, we must think of the surface as a dynamic entity in which the positions of the atoms are neither constant in time nor perfectly periodic in space, even under equilibrium conditions. The former phenomenon may be due to the diffusion of atoms, while the latter corresponds to the formation of a rough surface (atoms at the lattice positions parallel to the surface plane but displaced randomly in height) or surface melting (atoms at random positions with respect to all directions), which are frequent phenomena at temperatures close to the melting point of the solid. The surface is also home to a variety of localized excitations that have their own manifestations in the physical and chemical properties of surfaces, as will be seen.”