Body-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.
About this simulation
- What
- An interactive Chemistry simulation of Body-Centered Cubic Packing.
- Who
- Designed for AP, IB, and A‑Level Chemistry students.
- How
- Runs in any modern browser — drag, adjust, and explore in real time.
Updated 2026-03-25
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.