TABLE OF CONTENTS Solids are characterized by rigidity, incompressibility, slow diffusion, and mechanical strength. Also, unlike liquids and gases, solids have definite volume and shape.
The solid state has almost complete order. Solids are orderly because there is regular arrangement of the atoms, molecules or ions, and they are confined to small regions in the solids. They can not move very far away from their positions without disrupting the whole structure. The atoms, molecules or ions can have several different three dimensional arrangements and the result is a variety of geometrical structures. For example, diamond is composed of a single element, carbon, arranged in a three dimensional network that has a melting point of 3550 C. In contrast, solid agron melts at ?189 C and has a cubic close-packed structure whose atoms are held by weak van der Waal forces. A solid crystal generally has sharp boundaries with clear-cut shapes and the beautiful shape and color add to their value as gems.
The study of solid state begins with the observation of the shapes of crystals. This is known as geometric crystallography. In the mid-nineteenth century, crystal symmetry was described in terms of point lattice and this was followed by X-ray crystal structure determination by X-ray diffraction of crystals. Later on an important discovery in this field was the presence of lattice defects and their role in determining the properties of crystals.
When a substance is at such a low temperature that the thermal agitation of its...
