Description of adsorbate structures

If molecules adsorb to a crystalline surface they often form a crystalline overlayer which is called a superlattice. This occurs if the adsorbates bind preferentially to specific sites. Then the positions of the adsorbed molecules can be written as 

This together leads to the so-called Wood s notation A(hkl)c(p x q ) R/ — B, 

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One considerable obstacle to the use of gas-solid chromatography is a general lack of adequate descriptions of adsorbent structure, including information on the distribution and dimensions of pores. In addition, the lack of reproducibility of adsorbents, not only among manufacturers (different products, presumably the same) but also within the same manufacturer (different lots), provides a variability that hinders reproducible separation properties. 

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