This volume is one of four, each of which consists of reprinted chapters from the highly acclaimed, comprehensive two-volume set Intermetallic Compounds: Principles and Practice. published in 1995. In some cases the author or authors have added a brief addendum to bring their chapter up to date and in other cases more recent references have been added. Chapters have been selected and grouped in subject areas to provide more easily accessible and user-friendly volumes for individual researchers. The other titles in this four-volume set are: Crystal Structures of Intermetallic Compounds Basic Mechanical Properties and Lattice Defects of Intermetallic Compounds Structural Applications of Intermetallic Compounds