General Review of Phenomena and Processes

Abstract

In Part 1, the crystal structure was treated initially as an infinite, regular, three-dimensional array of atoms arranged on intersecting lattices. Although this mathematical concept underlies the entire discussion of the physical and chemical properties, it was necessary to abandon the concept of strict regularity to permit the description of substitutional and positional disorder. Furthermore, it was necessary to consider the termination of the crystal structure at surfaces, and to consider atomic displacements caused by strain between domains of different chemical composition. In this fourth part of the book, deviations from strict regularity will be treated more systematically. For each type of deviation a phenomenological description and, whenever possible, a theoretical interpretation will be given. Unfortunately, not all the atomic processes responsible for the macroscopic effects have been detected by experimental methods, and some theoretical interpretations are plausible rather than verifiable. Thus, it is not surprising that the literature is extremely confused, and that many ideas are still controversial. Nevertheless, it is essential for mineralogists and geologists to master the experimental data and the hypotheses since actual processes are governed not by equilibrium thermody-namics, but by local kinetics.