The DASH Procedure

This is based on the evaluation of the joint probability /7(Egr P), where Egj-denotes the extinction symbol, and P = (A, G... /n) are the correlated reflection intensities obtained from the linear least-squares Pawley refinement, when the most general extinction group of the crystal system under consideration is adopted. From Bayes s theorem  

The prior probability distribution (Egi-) is constant because all the extinction symbols are assumed to be equally probable / (P) is also constant because data do not change by varying the extinction group. Accordingly  

The normalized intensities Zh= EhP are submitted to statistical analysis for the determination of the space group symmetry. 

The algorithm provides a probability value for each extinction symbol compatible with the lattice symmetry established by the indexing procedure. 

Step 2 may be clarified by an example. In the orthorhombic system any space group may be represented by the string  

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