Tests of isomorphism: For two substances to be isomorphous with each other the following three criteria are to be satisfied: (a) The crystalline form should be similar. This is not a good criterion as there…

Isomorphism is an identity or close similarity in the crystalline form of substances typically containing dissimilar elements but having similar composition. It was recognized early in the study of crystals that crystals of similar constitution…

Liquid Crystals In a liquid, the molecules have no orderly arrangement. The molecules can move with respect to each other in a random manner, so liquids are able to flow. In a solid, the particles…

The Specific Heats of Solids (Dulong and Petit’s law) Dulong and Petit in 1819 observed that at room temperature and atmospheric pressure the product of the specific heats, CP and the relative atomic masses of…

Crystal detects The presence of defects to crystal lattice may profoundly influence the mechanical, electrical and optical properties of crystal. Reactively of the solids may also be explained by considering the defect structure. Crystal detects…

Defects in Solids A crystal is considered to be ideal or perfect if there is regular arrangement of lattice points, and there is no irregularity of any kind in the crystal lattice. Real crystals, however,…

The ‘hole’ concept and conductance At sufficiently high temperature a significant number of electrons in the valence band may gain enough thermal energy and promoted to the conduction band. The magnitude of the energy gap…

Semiconductors in Solid Materials The term semiconductor refers to those which have the weak conductivity at low temperatures but show increased conductivity as the temperature is raised. In such solids, the topmost filled valence band…

Insulators in Solid Materials A non-conductor or insulator has completely occupied lower band separated from the conduction band by a wide energy gap as schematically shown in Figure. At sufficiently high temperature the excitation of…

Conductors in Solid Materials The conductors are characterized by overlapping of either (i) partially filled valence band and the conduction band (Figure: a) or (ii) completely filled valence band and empty conduction band (Figure: b).…