Surface relaxations at mineral surfaces

A surface relaxation is a topology preserving distortion of a crystal surface. Investigations of simple models with harmonic interactions between planes of atoms, and simulations of the surface structure of crystals show that the distortion of the crystal structure at the surface is not restricted to the layers immediately adjacent to the surface, but instead the magnitude of the distortion decays exponentially with distance from the surface. Thus relaxations can mediate short range interactions between surfaces, destabilising symmetrical growth morphologies in favour of platelet morphologies. The relaxations that occur when a twin wall intersects a surface are also of interest since twin walls are sites of fast diffusion, high reactivity and novel properties. The surface structure of twin walls are affected by surface relaxations of the order parameter and by the coupling of secondary strains to the order parameter.