SOWOS: an open-source program for the three-dimensional Wulff construction

A Fortran90 program for the determination of the Wulff construction, starting solely from the directions of the bounding facets (defined by the user), is presented. SOWOS stands for solid of Wulff open source, and the program is distributed freely with no charge to the user, being readily available to the community for immediate use. Its simple algorithm (which will be explained) allows the determination of complex solids with hundreds of facets in just seconds on any machine, requiring only a small amount of memory. It is able to determine even the smallest facets and shortest edges and to distinguish almost adjacent vertices. The output files give a complete range of information about the structure: the coordinates of the vertices and the facets common to them, the extension of the facets and bounding vertices, and the length of the edges and extreme vertices. These details enable the reconstruction of the shape in any other (commercial) software for further processing. Visualization is straightforward via the free program gnuplot. A feature for the creation of cubic crystal atomistic models of the resultant solids is included. The program may be a useful tool for crystallography, nanostructures and any other field where crystal facets are involved.