Dislocations In Solids

This volume comprises the Proceedings of the Yamada Conference IX on Dislocations in Solids, held in August 1984 in Tokyo. The purpose of the conference was two-fold: firstly to evaluate the increasing data on basic properties of dislocations and their interaction with other types of defects in solids and, secondly, to increase understanding of the material properties brought about by dislocation-related phenomena. Metals and alloys, semi-conductors and ions crystals were discussed. One of the important points of contention was the electronic state at the core of dislocation. Another was the dislocation model of amorphous structure.

This volume comprises the Proceedings of the Yamada Conference IX on Dislocations in Solids, held in August 1984 in Tokyo. The purpose of the conference was two-fold: firstly to evaluate the increasing data on basic properties of dislocations and their interaction with other types of defects in solids and, secondly, to increase understanding of the material properties brought about by dislocation-related phenomena. Metals and alloys, semi-conductors and ions crystals were discussed. One of the important points of contention was the electronic state at the core of dislocation. Another was the dislocation model of amorphous structure.

This is the first volume to appear under the joint editorship of J.P. Hirth and F.R.N. Nabarro. While Volume 11 concentrated on the single topic of dislocations and work hardening, the present volume spreads over the whole range of the study of dislocations from the application by Kléman and his colleagues of homotopy theory to classifying the line and point defects of mesomorphic phases to Chaudhri's account of the experimental observations of dislocations formed around indentations. Chapter 64, by Cai, Bulatove, Chang, Li and Yip, discusses the influence of the structure of the core of a dislocation on its mobility. The power of modern computation allows this topic to be treated from the first principles of electron theory, and with empirical potentials for more complicated problems. Advances in electron microscopy allow these theoretical predictions to be tested. In Chapter 65, Xu analyzes the emission of dislocations from the tip of a crack and its influence on the brittle to ductile transition. Again, the treatment is predominantly theoretical, but it is consistently related to the very practical example of alpha iron. In a dazzling interplay of experiment and abstract mathematics, Kléman, Lavrentovich and Nastishin analyze the line and point structural defects of the many mesomorphic phases which have become known in recent years. Chapter 67, by Coupeau, Girard and Rabier, is essentially experimental. It shows how the various modern techniques of scanning probe microscopy can be used to study dislocations and their interaction with the free surface. Chapter 68, by Mitchell and Heuer, considers the complex dislocations that can form in ceramic crystals on the basis of observations by transmission electron microscopy and presents mechanistic models for the motion of the dislocations in various temperature regimes. While the underlying aim of the study of dislocations in energetic crystals by Armstrong and Elban in Chapter 69 is to understand the role of dislocations in the process of detonation, it has the wider interest of studying dislocations in molecular crystals which are ``elastically soft, plastically hard, and brittle''. Chaudhri in Chapter 70 discusses the role of dislocations in indentation processes, largely on the basis of the elastic analysis by E.H. Yoffe. The special case of nanoindentations is treated only briefly.

Dislocations are lines of irregularity in the structure of a solid analogous to the bumps in a badly laid carpet. Like these bumps, they can be easily moved, and they provide the most important mechanism by which the solid can be deformed. They also have a strong influence on crystal growth and on the electronic properties of semiconductors.

New materials addressed for the first time include the chapters on minerals by Barber et al and the chapter on dislocations in colloidal crystals by Schall and Spaepen. Moriarty et al extend the first principles calculations of kink configurations in bcc metals to high pressures, including the use of flexible boundary conditions to model dilatational effects. Rabier et al clarify the issue of glide-shuffle slip systems in diamond cubic and related III-V compounds. Metadislocations, discussed by Feuerbacher and Heggen, represent a new type of defect in multicomponent metal compounds and alloys. Kink mechanisms for dislocation motion at high pressure in bcc metals Dislocation core structures identified in silicon at high stress Metadislocations, a new type of defect, identified and described Extension of dislocation concepts to complex minerals First observations of dislocations in colloidal crystals

This is the first volume to appear under the joint editorship of J.P. Hirth and F.R.N. Nabarro. While Volume 11 concentrated on the single topic of dislocations and work hardening, the present volume spreads over the whole range of the study of dislocations from the application by Kléman and his colleagues of homotopy theory to classifying the line and point defects of mesomorphic phases to Chaudhri's account of the experimental observations of dislocations formed around indentations.Chapter 64, by Cai, Bulatove, Chang, Li and Yip, discusses the influence of the structure of the core of a dislocation on its mobility. The power of modern computation allows this topic to be treated from the first principles of electron theory, and with empirical potentials for more complicated problems. Advances in electron microscopy allow these theoretical predictions to be tested.In Chapter 65, Xu analyzes the emission of dislocations from the tip of a crack and its influence on the brittle to ductile transition. Again, the treatment is predominantly theoretical, but it is consistently related to the very practical example of alpha iron.In a dazzling interplay of experiment and abstract mathematics, Kléman, Lavrentovich and Nastishin analyze the line and point structural defects of the many mesomorphic phases which have become known in recent years.Chapter 67, by Coupeau, Girard and Rabier, is essentially experimental. It shows how the various modern techniques of scanning probe microscopy can be used to study dislocations and their interaction with the free surface.Chapter 68, by Mitchell and Heuer, considers the complex dislocations that can form in ceramic crystals on the basis of observations by transmission electron microscopy and presents mechanistic models for the motion of the dislocations in various temperature regimes.While the underlying aim of the study of dislocations in energetic crystals by Armstrong and Elban in Chapter 69 is to understand the role of dislocations in the process of detonation, it has the wider interest of studying dislocations in molecular crystals which are ``elastically soft, plastically hard, and brittle''.Chaudhri in Chapter 70 discusses the role of dislocations in indentation processes, largely on the basis of the elastic analysis by E.H. Yoffe. The special case of nanoindentations is treated only briefly.