PERIODIC3: a software package for the analysis of artificially anisotropic surfaces

Describes a computer code, for computing the reflectivity of corrugated periodic surfaces at all incidence angles, including skew incidences (i.e., the 2.5D problem). This is a self-contained code, and is available from the authors. Since the finite element method is employed for modeling the corrugations, the periodic cell can be of any shape and material composition, and this is one of the most attractive features of the finite-element and derivative methods. Metallic and non-metallic cells can be considered and, because a boundary integral is used for truncating the mesh, this hybrid approach is rigorous