Body-Centred Cubic
A cubic arrangement with particles at the eight corners plus one at the centre of the cell.
Formula / equation
2 atoms per cell, 68% packing
Unit
Dimensionless
In depth
The central atom belongs wholly to the cell, giving two atoms per cell, a coordination number of eight and 68% packing efficiency. The relatively open structure makes bcc metals somewhat less dense than close-packed ones and allows easy diffusion of small interstitial atoms such as carbon.
Examples in the real world
Alpha-iron, chromium, tungsten and all the alkali metals adopt the bcc structure.