Morphology of Metal Surfaces

The real surfaces of metals are relatively clean and better understandable compared with the surfaces of oxide materials, which are most frequently used in gas-solid chromatography of molecular inorganic compounds. 

At the atomic level, the smoothest observed surfaces of metal crystals still contain structures like those shown in Fig. 5.20. 

Yet some metallic surfaces with very small roughness could be reportedly produced outside of vacuum chambers [82], A layer of metal was consecutively polished with the colloidal slurries of silica and alumina. This procedure was followed by a multi-step cleaning from the slurry and residual metal particles by solutions of some chemicals. The roughness of a freshly deposited Pt surface characterized by grain sizes of 3 nm could be reduced to a rms of 0.1 nm. 

An adsorbed molecule would experience different adsorption potential when attached to a terrace, step or kink. On the other hand, on some metals (platinum as an example) the heats of adsorption of simple gases (ethylene, CO, H2) vary little with surface structure. Lee, et al. [84] examined the effect of surface reconstruction and relaxation on the electronic coordination numbers of the surface atoms. They found that highly stepped surfaces relax into a configuration where the surface atoms have about the same electronic coordination number as Pt(l 11) surface atoms. It means that they lack the coordinative unsaturation of the atoms, which would take place on unaltered stepped surfaces. 

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