A computer program, INDX, has been developed that attempts to index X-ray diffraction powder patterns by finding a reduced triclinic cell whose calculated Q values (Q = l/d2 ) match a desired percent¬age of the observed Q values within a given limit of error. If a reduced triclinic cell is found, the cell constants may be used to form a rectangu¬lar array, i.e., a Niggli matrix, and reference to published tables of general and special Niggli ma¬trices reveals whether or not the specific tri¬clinic cell may be transformed to a cell of higher symmetry.
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