On the incorrect assignment of space groups. I. Choosing the smallest primitive unit cell

Abstract

Deriving the smallest primitive unit cells, necessary to describe the translational periodicity of a crystal structure, is the first step toward choosing the correct space group. Among these smallest cells, only the reduced cell is unique and useful in selection of a Bravais lattice. Examples of both too small and too large a cell selected are illustrated, and the correct space groups and atomic coordinates are also given.