Crystals of layers are those formed by pile in a direction of perfectly periodic atomic layers in the other two directions. Solids with hexagonal, cubic centered in the faces and other structures belong to this class. Many metals, alloys, magnetic and ferroelectric materials, compounds of great practical interest as graphite, mica and clays, crystals of proteins and other macromolecules are included in this category.

The determination of the structure and defects of these systems, by X rays diffraction techniques, electrons, neutrons or other sources, is a very important scientific task, from the theoretical and practical point of view. It is particularly significant in order to understand the properties of these materials, the planar disorder that results from the defective pile of atomic layers.

The authors have developed a new method for the quantitative study of planar disorder in crystals of layers by diffraction techniques. It is based on an exact relation, mathematically demonstrated by them, between a function that characterizes the planar disorder and the diffraction pattern that is experimentally observed. It contains previous models as limit cases and it is applicable to any type of planar defect. Practical methodologies have been implemented to process diffraction data, transforming this way theoretical formalism into a tool of experimental work. The measurements carried out by the authors in intermetallic compounds used as permanent magnets and others of compact pile, are a part of this work, including five projects of National Laboratory of Luz Sincrotrón from Brazil.

These results constitute an original and important contribution to diffraction cinematic theory and its applications. They are endorsed by ten publications in high-level magazines and a contribution by invitation to the bulletin of the International Union of Crystallography (IUCR) dedicated to new tendencies of structural analysis. It also includes six reports on international events, among them, plenary oral presentations in the XIX Congress of the IUCR and in the VIII European Powder Diffraction Conference. The methodology has been requested by several European laboratories for its application and the authors were invited to present a seminar and to execute two measurement projects in the European Laboratory of Luz Sincrotrón.