Defects in the Crystal Lattice: Useful or Harmful?
At thermodynamic equilibrium crystals display some disorder due to the spontaneous generation of lattice defects, as we discuss in the case of lattice vacancies. Other examples of defects are color centers in ionic crystals and radiation damage in nuclear reactors. Understanding the role of dislocations in the mechanical properties of materials represented a great advance. Today, nondestructive materials testing has developed into an important field. Magnetic impurities and the Kondo effect are discussed.