Material undergoes the transformation from metal to non-metal or from non-metal to metal when environmental conditions, such as temperature and pressure, or the percentages of constituent components are changed. Such a transition is known as the metal-nonmetal M-NM transition.This book, The Physics of Metal Nonmetal Transitions, explores the mechanisms so far discovered which cause the M-NM transition and presents a systematic discussion of them. All the mechanisms are discussed in terms of energy bands, and the band theory is introduced and explained in chapter 2. Once chapters 1 and 2 have been assimilated, the remaining chapters can be