Crystal Structures

Radius ratio (r_cation / r_anion)

trigonal tetrahedral octahedral cubic

To maximise electrostatic attractions, ions surround themselves with as many oppositely charged ions as possible. The radius ratio rules relate the structure adopted to the relative size of the cation and anion. A cation must be in contact with its anionic neighbours for a structure to be stable. If a cation is too small, a lower coordination number is likely to be more stable. Use the slider to change the ratio of the cation to anion radius. Use the buttons to change the coordination type.