关于空间群判断失误的札记I.最小素单胞的选取

On the Incorrect Assignment of Space Groups. I. Choosing the Smallest Primitive Unit Cell

导出反映晶体结构周期的最小素单胞是正确判断空间群的第一步，其中以还原单胞的选择最为理想。它不仅具有选择的唯一性，且便于确定布拉维格子的类型。本文还讨论单胞选取过小和过大的实例，并给出正确的单胞和空间群以及原子坐标。

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.\;