Inorganic Crystal Structures

radius ratio < 0.225

coord = 3, trig planar

radius ratio = 0.225 → 0.413

coord = 4, tetrahedral

radius ratio = 0.414 → 0.731

coord = 6, octahedral

radius ratio = 0.732 → 0.999

coord = 8, cubic

radius ratio = 1

coord = 12, close-packed

Rock Salt

CCP Anions, octahedral holes filled, coord = 6

CsCl

Primitive Cubic Array Anions, coord=8

NiAs

HCP (distorted) Anions, Octahedral holes filled, coord=4

Wurztite

HCP anions, ½ tetrahedral holes, coord=4

Zinc Blende (ZnS) also known as Sphalerite Structure

CCP anions, ½ tetrahedral holes filled, coord=4