Reciprocal Space Mapping
Crystals that are highly perfect will diffract over a very small angular range and therefore require very high angular resolution x-ray techniques to extract detailed structural information. The aim of this paper is to discuss the use of reciprocal space mapping or diffraction space mapping as a route to extracting very detailed structural information from high quality crystals. In fact much information is obscured by standard diffraction profile analysis methods unless significant assumptions are made to interpret the data. Reciprocal space mapping has not been confined to highly perfect crystals but has yielded detailed understanding of polycrystalline samples, (Fewster and Andrew, 1996). The conventional “powder diffraction” methods yield little detailed information because of the swamping effects of the ill-defined diffraction probe. The well defined probe of the high resolution diffractometer to be described is important for analysing ill-defined samples. Only when the analysist is sure of the assumptions about the structure should a less well defined probe be used. The aim of this paper though is to show how an enormous quantity of structural information from multiple crystal diffractometric methods can be extracted using reciprocal space mapping. The relationship between the resultant diffraction pattern and the real structure will be discussed and how with the aid of additional tools it is possible to come closer to a truer picture of the structure. This paper will be confined to high angular resolution techniques. Low resolution diffraction space mapping has its advantages for mapping very large areas of reciprocal space and for very imperfect samples (Fewster and Andrew, 1996, 1993a).
KeywordsReciprocal Lattice Reciprocal Space Diffraction Plane High Angular Resolution Axial Divergence
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