f centre in defects of crystals

Defects in Crystals - According to third law of thermodynamic it is only at OK that true crystals passes perfect order of arrangement of atoms in pure crystals. But with rise in temperature some derivations from complete order takes place. Presence of impurit..

According to third law of thermodynamic it is only at OK that true crystals passes perfect order of arrangement of atoms in pure crystals. But with rise in temperature some derivations from complete order takes place. Presence of impurities also adds to disorde..

The defect, which arises due to the irregularity in the arrangement of atoms or ions are called point defects..

The ionic crystals consist of positively and negatively charged ions arranged in a regular fashion throughout the crystal. They form a network of positive and nagative ions in three dimension in such a way that cations and anions occupy alternate sites. These are held together ..

Stoichiometric Defects - If imperfections in the crystal are such that the ratio between the anions and cations remain same as represented by the molecular formula, the defect is called a stoichiometric defect. There are three types of stoichiometric def..

In in ionic crystal of the type A + B - , equal number of anions and cations are missing from the lattice sites so that electrical neutrality is maintained it is called schottky defect. fig 2.29 - Schottky defect..

Suppose the magnitude of the forces between the particles is F. As the only force acting on A towards B, is F, its acceleration is The force on B is (-F) and hence, Substituting this in equation (1) This means, the velocity of the centre of mass..

Magnitude of Crystal Field Splitting - Different ligands differ in their ability to produce a splitting of the d-orbitals. For e.g., strong lewis bases, such as CN - and NH 3 , produce a strong field. They repel d electrons most strongly and cause a greater separation of the two groups (t..

As the number of ions decrease, volume is the same, so density decreases. Crystals with Schottky defect conduct electricity to a small extent. Due to the presence of holes the stability of the crystal decreases..

In case of ionic solids, the impurities are introduced by adding impurity of ions. If the impurity ions are in a different oxidation state from that of the host ions, vacancies are created. For e.g., If molten NaCl, containing a little of SrCl 2 as impurity is allowed to cool, in the crystal..