Crystal Chemistry of Ionic Materials (Part 2: Polyhedral Models)

This 3-part tutorial series on the crystal chemistry of ionic materials provides an overview of the principles behind ionic crystal structures and their representation using polyhedral models. The series is designed for an introductory undergraduate materials science course and assumes some prior exposure to close-packed metal structures. In the second part, we delve into more complex ionic structures and introduce the polyhedral model. Unlike traditional ball-and-stick models, the polyhedral representation is more effective in illustrating the intricate structures of ionic materials such as TiO₂, Al₂O₃, and MnO₂. We’ll explore how, using straightforward principles, materials that may initially appear distinct can actually share closely related crystal structures.