Body-centered cubic

Definition

Body-centered cubic (BCC) is a type of crystal structure characterized by a cube with an atom at each of the eight corners and one atom positioned in the center of the cube. This arrangement results in a unique coordination number and packing efficiency, influencing the physical properties of materials, such as strength and ductility.

5 Must Know Facts For Your Next Test

1. In a body-centered cubic structure, each unit cell contains two atoms due to the contribution of the corner atoms and the center atom.
2. The BCC structure has a coordination number of 8, meaning each central atom is surrounded by eight other atoms.
3. Materials with a body-centered cubic structure tend to have high strength but lower ductility compared to face-centered cubic materials.
4. The atomic packing factor for BCC is approximately 0.68, which indicates that about 68% of the volume is occupied by atoms.
5. Common metals that crystallize in a body-centered cubic structure include iron at room temperature, chromium, and tungsten.

Review Questions

• How does the body-centered cubic structure influence the mechanical properties of materials?
  • The body-centered cubic (BCC) structure impacts mechanical properties such as strength and ductility due to its unique atomic arrangement. The presence of an atom in the center of the cube adds stability to the structure but results in lower packing efficiency compared to face-centered cubic structures. This leads BCC materials to generally exhibit higher yield strength but lower ductility, making them more brittle under stress.
• Compare and contrast body-centered cubic and face-centered cubic structures in terms of atomic arrangement and properties.
  • Body-centered cubic (BCC) structures feature an atom at each corner and one in the center, resulting in lower packing efficiency (approximately 68%) and a coordination number of 8. In contrast, face-centered cubic (FCC) structures have atoms at corners and centers of faces, leading to higher packing efficiency (around 74%) and a coordination number of 12. Consequently, FCC materials typically demonstrate higher ductility while BCC materials are stronger but more brittle.
• Evaluate the significance of coordination number in relation to the body-centered cubic structure's overall stability and material properties.
  • The coordination number plays a crucial role in determining the stability and material properties associated with body-centered cubic structures. With a coordination number of 8, each central atom is surrounded by eight nearest neighbors, contributing to its overall stability. However, this lower coordination number compared to other structures like face-centered cubic affects how BCC materials respond to external forces, resulting in enhanced strength but diminished ductility. Understanding this relationship helps predict material behavior in applications such as construction or manufacturing.

Related terms

Face-centered cubic: A crystal structure where atoms are located at each of the corners and at the centers of all the faces of the cube, leading to a higher packing efficiency compared to BCC.

Crystal lattice: The three-dimensional arrangement of atoms in a crystalline solid, defining the geometric pattern of the structure.

Coordination number: The number of nearest neighbor atoms surrounding a central atom in a crystal structure, which influences its properties.