XRAYSCAN - AN INDEXING PROGRAM CONSIDERING DENSE SPURIOUS PEAKS IN ANOPTIMIZATION METHOD

An indexing algorithm has been developed with an optimization method w hich takes spurious peaks into account. With the suggested indexing fu nction, a Pascal-written program, XRAYSCAN, is able simultaneously to index and refine the powder diffraction data containing many spurious peaks. XRAYSCAN finds all possible solutions for the lattice parameter s by the Monte Carlo, or random searching method, and refines the raw solutions by Powell's method for accurate lattice parameters. At the p resent time, XRAYSCAN is capable of analyzing materials with either cu bic, tetragonal, hexagonal, tetragonal, or orthorhombic structures on an IBM PC. A tetragonal Mn3O4 example with four spurious peaks is used to demonstrate the accuracy and capability of the program to identify spurious peaks. In spite of two unidentified spurious peaks, the accu racy of the XRAYSCAN solution is only slightly affected (< 10(-3) %) a fter arbitrarily adding 13 spurious peaks to the peak Mn3O4 pattern.