Overview

Wulffman is a program for interactively examining the Wulff shapes of crystals with specified symmetries. The Wulff shape is the shape that possesses the lowest surface energy for a fixed volume, and hence represents the ideal shape that the crystal would take in the absence of other constraints. For a periodic crystal, i.e. one that can be generated by periodic repetition of a simple unit cell , the Wulff shape must be consistent with the crystallographic point group symmetry of the underlying crystal. The point group is simply the set of all point isometries (rotations, roto-inversions, and reflections) that leave the environment around a point unchanged. In the most general case, the Wulff shape will be a convex polyhedron whose faces (facets) correspond to crystal planes that are low in energy.

Wulffman requires the point group symmetry of a crystal of interest, a set of crystal planes (facets), and their respective surface energies. From this information, Wulffman constructs the Wulff shape and sends its output to Geomview , a 3-D visualization tool. Surface energies can be changed at will, and Wulffman reconstructs the lowest energy polyhedron. In this manner, the user can directly and easily visualize the effects of surface energy anisotropy on the equilibrium forms of crystals.

Wulffman Home Page