Structural diffusion, interface structure and crystal growth

Abstract

A description is developed of the structure of the interface between a crystal and its melt, and of the growth of a crystal in such a situation, which concentrates attention exclusively on the liquid side of the interface. It is concluded that structural effects extend to at least a distance of 20 Å from the interface and that the interfacial free energy can be accounted for almost entirely by entropy loss in the liquid. A criterion is derived for surface roughness which has some relation to the similar criterion derived by Jackson. The theory is then applied to the growth of a crystal from its melt and an expression is derived for the minimum defect concentration in the crystal. It is concluded that the defects are largely vacancies or interstitial atoms and on this basis a calculation is made of the minimum dislocation density. This quantity is shown to increase linearly with growth velocity. Finally the theory is applied to consideration of the possible production of vitreous solids by very rapid freezing. As an illustrative example, calculations are given for the case of the water-ice interface. Show more