Solving a Structure in the Reciprocal Space, Real Space and Both by Using the EXPO Software

The solution of crystal structures from X-ray powder diffraction data has undergone an intense development in the last 25 years. Overlapping, background estimate, preferred orientation are the main difficulties met in the process of determining the crystal structure from the analysis of the one-dimensional powder diffraction pattern. EXPO is a well known computer program that, designed for solving structures, organic, inorganic, as well as metal-organic by powder diffraction data, employs the two most widely used kinds of solution methods: Direct Methods proceeding in the reciprocal space and Simulated Annealing proceeding in the real space. EXPO allows also to suitably combine these two approaches for validating the structure solution. In this paper, we give examples of structure characterization by EXPO with the aim of suggesting a solution strategy leading towards the application of reciprocal-space methods or real-space methods or both.