Body-centered cubic unit cell

Definition

A body-centered cubic (BCC) unit cell is a type of crystal structure in which each cube-shaped unit cell has an atom at each of its eight corners and one atom at the center. The BCC structure is less densely packed than the face-centered cubic (FCC) structure but more so than the simple cubic (SC) structure.

5 Must Know Facts For Your Next Test

1. Each body-centered cubic unit cell contains a total of 2 atoms: 1/8th of an atom from each of the 8 corners and 1 whole atom at the center.
2. The coordination number, which is the number of nearest neighbors, for a BCC structure is 8.
3. The packing efficiency of a BCC structure is approximately 68%, meaning that 68% of the volume in a BCC crystal is occupied by atoms.
4. Examples of elements with a BCC crystal structure include iron (at room temperature), chromium, and tungsten.
5. The edge length $a$ and atomic radius $r$ relationship for a BCC unit cell is $a = \frac{4r}{\sqrt{3}}$.

Review Questions

• How many atoms are there in a single body-centered cubic unit cell?
• What is the coordination number for a body-centered cubic unit cell?
• Provide an example of an element that crystallizes in a body-centered cubic structure.

Related terms

Face-Centered Cubic Unit Cell: A type of crystal structure with atoms located at each corner and in the center of each face of the cube, leading to higher packing efficiency than BCC.

Simple Cubic Unit Cell: A simplest form of crystal lattice where atoms are situated only at the corners of each cube, resulting in low packing efficiency.

Coordination Number: The number of nearest neighbor atoms or ions surrounding an atom or ion in a crystal lattice.