1 Thermodynamic Properties of Solids : Experiment and Modeling

While thinking of thermodynamic properties of solids, a wide variety of properties and phenomena come to mind. Perhaps the most notable are specific heat, phase transitions, thermal expansion, thermal conductivity, melting, and so on. The macroscopic thermodynamic properties [1–11] are determined by microscopic crystalline and electronic structure and atomic vibrations, and these are determined by the nature of bonding between the atoms. In this book, we focus on the understanding and modeling of these microscopic and macroscopic properties and the experimental techniques [12–21] used in their investigation. The modeling of the structure, dynamics, and various thermodynamic properties is done either by the first-principles quantum mechanical methods [6, 7] or by the semiempirical methods [8–11] largely based on models of interatomic interactions. The former is computationally far more intensive; therefore, its application to complex structures has been more recent and somewhat limited because of the available computational resources. The latter has been more widely used. Both of these techniques are extensively covered in this book. On the experimental side, a variety ofmicroscopic andmacroscopic techniques are in use. The visible light, infrared and X-ray photons, and thermal neutrons are most widely used microscopic probes. These spectroscopic techniques [12–17] generate a rich amount of complex data of all kinds of vibrationalmodes of various polarizations and symmetry. Theoretical lattice dynamical calculations [7–10] are necessary for optimal planning of the experiments and for the microscopic interpretation of complex experimental data. Macroscopic measurements of specific heat [18] and thermal expansion [19, 20] and use of high-pressure, high-temperature devices [21] are also particularly important for thermodynamic investigations. These experimental techniques and the interpretations of their results by theoretical techniques are presented in individual chapters.