Chapter 8 Thermodynamics of point defects

Abstract

This chapter highlights the thermodynamics of point defects. It considers a monoatomic solid at a temperature T that has a volume V and is under an external pressure P . Thermodynamics demands that this solid contain a number of vacancies. In the simplest case, it contains only monovacancies. In the thermodynamics of point defects, the fundamental point is to compare the functions G, H, and S of the real crystal with the corresponding functions G 0 , H 0 , and S 0 of a perfect crystal with the help of appropriate parameters. Varotsos and Alexopoulos chose the two perfect states (crystals)—namely, (1) the isobaric perfect crystal and (2) the isochoric perfect crystal. A perfect crystal is compared with a real crystal of the same (external) pressure and temperature. As the real crystal should contain, n vacancies, its volume V generally differs from the volume V 0 of the perfect crystal. This perfect crystal is defined as an isobaric perfect crystal , and the defect parameters are consequently defined by considering the creation of n vacancies under conditions of constant temperature and pressure. On the other hand, a different perfect crystal is compared to a real crystal of the same volume and temperature. The perfect crystal is called an isochoric perfect crystal , and the creation of n vacancies is then considered under conditions of constant temperature and volume.