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

In this paper we report results showing that surface relaxations may profoundly alter the equilibrium growth morphology of crystals. This may result in growth forms not predicted by the Wulff plot. Surface relaxations and polarization fluctuations produce extra terms in the free energy of a growing crystal nucleus which combine with the surface energy to produce an effective surface energy which depends on the size and shape of the crystal. We consider the case of the growth of nuclei of a crystal with cubic symmetry and show that if the surface relaxations are large enough then small nuclei will 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.