Punctual defects

The Perez model comes from an approach in which the source of mobility is the existence of quasi-punctual defects characterized by positive or negative fluctuations of packing density, whereas classical free volume theories take into account only the domains of low packing density, e.g., the holes. The model leads to the following equation for the complex modulus ... 

In Chapter 5, we described in detail the effect on the diffiracted intensity s distribntion of the discrepancies between a crystal s mean stmcture and its actual structure. The quantitative study of these effects makes it possible to accurately determine the density of punctual defects, of dislocations or of stacking faults, the size of the grains, as well as the microstrain rate, etc. This type of analysis was developed in the second half of the 20 century and, due to the tremendous progress made by computers, became widespread in the late 1980s. In 1999, the International Union of Crystallography published a book describing most of the aspects of microstractirral analysis by X-ray diffraction on polycrystalline samples [SYN 99],... 

Let us consider an ensemble composed of quantum objects such as molecules, atoms, punctual defects of a solid and of nuclei, protons, electrons... 

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