Effect of surface relaxations on the equilibrium growth morphology of crystals: platelet formation

In this paper we report results showing that surface relaxations may profou ndly alter the equilibrium growth morphology of crystals. This may result i n growth forms not predicted by the Wulff plot. Surface relaxations and pol arization fluctuations produce extra terms in the free energy of a growing crystal nucleus which combine with the surface energy to produce an effecti ve surface energy which depends on the size and shape of the crystal. We co nsider the case of the growth of nuclei of a crystal with cubic symmetry an d show that if the surface relaxations are large enough then small nuclei w ill grow into platelets, although large nuclei still grow into large three- dimensional crystals. We show by considering materials with the perovskite structure that this effect may occur in real materials.