Combined Analysis

Introduction

Recent developments in solid state chemistry and technology have made intensive structural analysis from single crystal diffraction a necessity. However, for many solids, single crystal growth is not easily undertaken and is sometimes impossible. When this is the case, or when structural defects cannot be overcome, the corresponding phases often have to be forsaken, due to the inherent difficulties of performing crystallographic characterization of polycrystals. Recently, powder diffraction techniques have progressed significantly, notably due to the Rietveld approach [RIE 69] and developments in computer science. Undoubtedly these developments are important in the study of solids that do not form large crystals, but also of all materials elaborated by classic solid state reactions, thin deposited structures, natural materials, such as clays, and more recently, nanomaterials in which the required properties are intimately linked to the stabilization of small crystals.

Since the publication of Rietveld’s method, several tens of thousands of structures have been refined and thousands have been resolved ab-initio from only the diffraction data of powder samples. The number of laboratories and industries using this technique, which is still fairly new when dealing with the incorporation of various formalisms as used in the combined approach, continually increases.

However, materials with specific properties are often elaborated from low symmetry phases, which are consequently ...