CHEM 001B Lecture Notes - Lecture 13: Crystal Structure, Sphalerite, Zinc Sulfide
Document Summary
A cation"s size and the shape of the hole occupied by the compound are directly. Tetrahedral hole: cation radius is about 22. 5 to 41. 4% of the anion radius. Octahedral hole: cation radius is about 41. 4 to 73. 2% of the anion radius. Cubic hole: cation radius is about 73. 2 to 100% of the anion radius. Ionic compounds with similar-sized cations and anions, such as cscl, usually form a simple cubic structure. They can be described by unit cells with either cations at the corners or anions at the corners. Cubic closest-packing (fcc) of cl - ions with na + ions in octahedral holes (rock salt structure) Sphalerite: fcc unit cell of s 2- with the zn 2+ in four of the eight tetrahedral holes. Fluorite: ca 2+ ions form an expanded fcc array to accommodate the larger f - ions, which occupy all eighth tetrahedral holes.
