Structure, growth and morphology of crystals*

Abstract

The structural properties necessary for a crystal face to grow layer after layer are considered. The growth layer (slice) must have a minimum thickness d hkl and therefore the same composition as the crystal. The slice must contain periodic bond chains in at least two different directions. For ionic crystals the slice should not have a dipole moment perpendicular to its plane. It is found that sometimes a particular intermittent way of growth can occur when there are two or more equivalent periodic bond chains per primitive cell. The character of these faces is between flat and stepped. The structural properties of periodic bond chains are considered. These chains are determined by the intersection of two slices. This explains the unequal development of parts of one zone since, for different parts, the chains are not necessarily the same. The effect of pseudosymmetry on the character of a face is pointed out. Finally a practical method is given that allows one to derive from the structure all the faces that can grow layer after layer.