TABLE OF CONTENTS In this Chap. 5 of the book on Thermal Analysis of Materials, the link between microscopic and macroscopic descriptions of crystals is given in Sects. 5.1 3. This is followed by a thermodynamic analysis of melting of crystals and isotropization of mesophases in terms of entropy and enthalpy in Sects. 5.4 and 5.5. The final section deals with the properties of liquids and glasses (Sect. 5.6).
Crystals have always fascinated man. To this day crystals are not only treasured because of their beauty [1], but there remain some of the ancient beliefs of possible magic. Huygens' drawing of a CaCO 3 crystal in Fig. 2.101 was first prepared to explain the occurrence of the birefringence more than 100 years before Dalton's proof of the existence of atoms (see Sect. 1.1.1). Even earlier suggestions exist of links between the external regularity of crystals, depicted in Fig. 3.77, and the atomic structure. Kepler analyzed in 1611 the hexagonal structure of snow flakes, as shown in Fig. 5.1 in terms of regularly packed balls, and Hooke (1665) used bullets to understand the shapes of diamonds. The correct NaCl structure could be derived 100 years ago purely from packing consideration of spheres of different radius and charge, as reproduced in Fig. 5.2. All leads to the conclusion that motifs must repeat themselves regularly in space. Today we know about the details of the structure of the motifs and their arrangement in the crystals through X-ray diffraction, as can...
