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chemistry/body-centered-cubic-packing
View PricingBody-Centered Cubic Packing
Explore how one center atom boosts packing from 52% to 68%. Understand the body diagonal, coordination number 8, and why alkali metals use BCC.
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Key Concepts
Body-Centered Atom
One complete atom sits at the very center of the cube, in direct contact with all 8 corner atoms.
Coordination Number 8
The center atom is surrounded by 8 nearest neighbors at the cube corners. All contacts are along body diagonals.
Body Diagonal Contact
Atoms touch along the space diagonal of the cube: √3·a = 4r. This gives 68% packing efficiency with 2 atoms per unit cell.
Understanding Body-Centered Cubic Packing
**Body-Centered Cubic (BCC)** packing is a common metallic crystal structure that improves significantly on simple cubic packing by inserting an additional atom at the center of the cube.
The center atom is in contact with all 8 corner atoms along the **body diagonal** of the cube. This gives a **coordination number of 8** and increases the **packing efficiency to 68%** — a substantial improvement over SC's 52%.
BCC is the preferred structure for many important metals including **Lithium, Sodium, Potassium, Chromium, Tungsten**, and **Iron (α-Fe below 912°C)**. Understanding BCC is essential for predicting metallic properties.