AB-INITIO STRUCTURE DETERMINATION FROM POWDER DATA USING DIRECT-METHODS

An ab initio structure determination was carried out on the basis of p owder data using the programs developed by Jansen, Peschar and Schenk [J. Appl. Cryst. (1992a), 25, 231-236; J. Appl. Cryst. (1992b), 25, 23 7-243; Z. Krist. (1993), 206, 33-43]. The results give a very good app roximation to the single crystal structure. The main problems in struc ture determination from powder data so far are the determination of th e correct space group and a better possibility than Rietveld refinemen t to refine the structural model coming out of the direct methods.