Cubic crystal system

Lore & Background

The cubic crystal system is defined by a unit cell shaped like a cube. It has three Bravais lattices: primitive cubic (cP), body-centered cubic (cI), and face-centered cubic (cF). The primitive cubic lattice has one lattice point per unit cell, body-centered cubic has two, and face-centered cubic has four. The face-centered cubic lattice is closely related to the hexagonal close packed system, differing only in the relative placements of hexagonal layers. Attempting to create a base-centered cubic lattice results in a simple tetragonal Bravais lattice.

Reader's Guide

The cubic crystal system is significant because it describes the atomic arrangement of many common elements and compounds. Primitive cubic structures are rare, found in polonium, while body-centered cubic and face-centered cubic structures are common in metals like iron, chromium, tungsten, aluminium, copper, gold, and silver. The system also includes important multi-element structures such as the caesium chloride structure (space group Pm3m), the rock-salt structure (space group Fm3m), and the fluorite structure. The caesium chloride structure is often confused with body-centered cubic but has two different atomic species. The rock-salt structure consists of two interpenetrating face-centered cubic lattices forming a checkerboard pattern. These structures are fundamental to understanding the properties of many crystalline materials, from alkali halides to transition metal oxides.

Did You Know?

• The face-centered cubic lattice is not necessarily close-packed when a motif is set onto the lattice points, as seen in diamond and zincblende lattices.
• The caesium chloride structure has a coordination number of eight for each ion.
• The rock-salt structure has octahedral coordination, with each atom having six nearest neighbors of the opposite type.