Band Theory of Solids

Abstract

The free electron models of metals that we have presented in the preceding chapter gives us a good deal of insight into several properties of metals. Yet there are many other important properties that these models do not explain. In particular, they do not tell us why, when chemical elements crystallize to become solids, some are good conductors, some are insulators, and yet others are semiconductors with electrical properties that vary greatly with temperature. These differences are not minor, but rather remarkable. The resistivity may vary from ρ ~ 10−8 ohm-m for a good conductor to ρ ~ 1022 ohm-m for a good insulator.