# WulffPack: A Python package for Wulff constructions

J. M. Rahm
and
P. Erhart

*Journal of Open Source Software* **45**, 1944
(2020)

doi: 10.21105/joss.01944

WulffPack is a Python package that carries out the Wulff construction and its generalizations using an efficient algorithm based on calculation of the convex hull of the vertices of the dual of the Wulff polyhedron. The user provides surface energies and crystal symmetry and WulffPack returns a versatile object that, at its core, contains the coordinates of the Wulff shape. Extraction of symmetry operations is handled internally with spglib. WulffPack includes functionality for visualizing the constructed shapes using Matplotlib. There are also functions for analyzing the constructed shape, most notably in terms of area fraction of symmetrically inequivalent facets. This quantity is important in applications where properties of the material are facet-dependent, such as in catalysis. Finally, using the Atomic Simulation Environment, an atomistic representation of the Wulff shape can also be extracted. An extensive user guide including a documentation of the API is available at http://wulffpack.materialsmodeling.org/.