Alkali-aluminium surface alloys

In this Chapter, we focus on alkali-aluminum surface alloys where the geometrical structure has been determined in detail. As can be seen from Table 1, which contains a list of the adsorbed phases formed by adsorption of alkali metals on aluminium surfaces, this limitation is not a serious restriction, since studies exist for a quite a number of low index aluminum surfaces and alkali metals. Although most of the structures of the phases listed in Table 1 have been determined by low energy electron diffraction (LEED), the crucial, first observation of substitutional adsorption for alkali-aluminium systems was made in a combined surface extended x-ray fine structure (SEXAFS) and density functional theory (DFT) study of the Al(l 11)—(v 3 x 3)7 30°—Na phase formed by adsorption of 1/3 ML Na at room temperature by Schmalz et al [7] in 1991. The structure of the Al(lll)-(4 x 4)—Na phase was also determined by SEXAFS. 

As described in Sec. 1.2, the first observation of surface alloy formation for alkali-aluminium systems was made in 1991 in a combined SEXAFS and DFT study of the Al(l 11)—(v 3 x. 3)./ 30°—Na phase formed by Na adsorption on Al(lll) at room temperature. The surface structure resulting from the calculations is compared with the experimental results in Table 16. As can be seen... 

Surface alloys formed by adsorption of alkali metals on aluminium surfaces. 

In this chapter we have concentrated on surface alloy systems for which there exists rather complete and quantitative stmctural information, but have also concentrated on relatively simple structures for which a fairly consistent picture with respect to the surface rumpling has been found. One group of such surface phases which we have not discussed are those formed by alkali metal adsorption on aluminium because there is such a huge difference... 

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