At the dawn of structural crystallography, Walther Friedrich, Paul Knipping and Max von Laue carried out the first experiments and developed the theory of X-ray diffraction. From the early days, when even the simpler inorganic structures filled an entire PhD study, structural crystallography evolved at its own pace and found new partners in chemistry, physics, materials science, biology and other fields of physical sciences. Both morphological and structural crystallography, however, have remained as important instruments in the mineralogist’s toolbox until today. Efforts to enhance the existing instrumentation, to improve our understanding of the theory of diffraction, to study nanoparticulate or poorly ordered materials, and to master large, complex structures continue in all fields of physical sciences. Mineralogy can thus use the fruits of this labour and include them in its toolbox.
Aperiodic mineral structures
Published:January 01, 2017
The three-dimensional periodic nature of crystalline structures was so strongly anchored in the minds of scientists that the numerous indications that seemed to question this model struggled to acquire the status of validity. The discovery of aperiodic crystals, a generic term including modulated, composite and quasicrystal structures, started in the 1970s with the discovery of incommensurately modulated structures and the presence of satellite reflections surrounding the main reflections in the diffraction patterns. The need to use additional integers to index such diffractograms was soon adopted and theoretical considerations showed that any crystal structure requiring more than three integers to index...