Crystal Growth

Crystal growth may occur naturally or through artificial processes and crystal is solid material whose constituent atoms are arranged in an orderly recurring pattern extending all three spatial aspects. In other words crystal growth comes in processes happening in series. Diffusion of the atoms of the crystallizing substance through the nearby environment to the surface of the crystal is one way. Diffusion of these atoms over the surface of the crystal to particular sites on the surface, incorporation of atoms into the crystal at these sites and the diffusion of the heat of crystallization away from the crystal surface.

Ehrenfest’s classification

The growth rate may be subjected by the above said procedures and the initial formation of the centers form which crystal growth proceeds is referred to as nucleation. Crystalline solids are usually formed by cooling and solidification from the molten state. Ehrenfest’s classification of first order phase transitions and there is discontinuous change in volume at the melting point. Looking into the context, the crystal and melt are different phases with an interfacial discontinuity having a surface of tension with a positive surface energy.

The growing monolayer

The potential energy of a crystal seems to be less in forms including the fewest possible ledge sites. This means that, in a system of usual crystal growth, dilute fluid and modest departure from equilibrium the crystal faces of the growth form are likely to be tightly packed and atomically smooth. There will be critical size of monolayer, which will be a decreasing function of super-saturation in a way all monolayer smaller than the critical size seem to contract out of existence and such are larger that will grow to a absolute layer.

Chance for critical fluctuations

Kinetic analyses denote that the possibility of critical fluctuations is tiny that in finite systems ideal crystals will not grow excluding at substantial departures from equilibrium. And in ordinary experience finite crystals do grow in a usual system only at infinitesimal departures from equilibrium is described by the screw dislocation theory. According to the theory the crystal growth is kept by permanent surface ledges which result from the appearance of screw dislocations in the crystal face.

When the departures from equilibrium are sufficiently large and the more usual growth shapes become unbalanced and cellular progress. Importantly the progress of protuberances on a primarily regular crystal permits more efficient removal of latent heat or of impurities but at the cost of higher interfacial region and he associated excess surface energy.

Questions:

• What is crystal growth?
• State the significance of crystal growth.