Face-centered cubic

Definition

Face-centered cubic (FCC) is a type of crystal lattice structure where atoms are located at each of the corners and the centers of all the faces of the cube. This arrangement allows for a highly efficient packing of atoms, leading to significant properties like high ductility and strength in materials. FCC is one of the most common structures in metallic solids, facilitating unique interactions between atoms.

5 Must Know Facts For Your Next Test

1. In a face-centered cubic structure, each unit cell contains four atoms: one from each of the eight corners and one from each of the six face centers.
2. The coordination number for face-centered cubic is 12, meaning each atom has 12 nearest neighbors.
3. Common metals that adopt the FCC structure include aluminum, copper, gold, and silver.
4. FCC crystals exhibit a higher packing efficiency of about 74%, which is one of the highest among crystal structures.
5. The face-centered cubic structure plays a crucial role in determining the physical properties of metals, including their malleability and conductivity.

Review Questions

• Compare and contrast the face-centered cubic structure with other types of crystal lattice arrangements, such as body-centered cubic and hexagonal close-packed structures.
  • The face-centered cubic (FCC) structure differs from body-centered cubic (BCC) and hexagonal close-packed (HCP) structures primarily in their atomic arrangements and packing efficiency. FCC has atoms located at each corner and center of each face, resulting in a coordination number of 12 and higher packing efficiency (74%). In contrast, BCC has a coordination number of 8 with lower packing efficiency (68%), while HCP has similar packing efficiency to FCC but features a different geometric arrangement. These differences significantly influence the mechanical properties and behavior of materials formed by these structures.
• Evaluate how the atomic arrangement in a face-centered cubic structure influences the physical properties of metals that exhibit this lattice type.
  • The atomic arrangement in a face-centered cubic (FCC) structure contributes to various physical properties such as ductility and malleability. The close-packing nature allows for easier movement of dislocations within the lattice, enabling metals like copper and aluminum to deform under stress without breaking. Additionally, the high coordination number leads to strong metallic bonding between atoms, which enhances strength while maintaining ductility. As a result, FCC metals are often used in applications requiring both flexibility and resilience.
• Synthesize information about how different crystal structures impact the behavior of materials under varying temperatures and pressures.
  • Different crystal structures, including face-centered cubic (FCC), can greatly affect material behavior under varying temperatures and pressures due to their unique arrangements of atoms. For instance, FCC metals typically maintain their ductility even at elevated temperatures because their close-packed nature allows for more slip systems during deformation. In contrast, BCC metals might become brittle at low temperatures due to fewer slip systems available for dislocation movement. Understanding these differences is critical for engineering applications where materials must withstand harsh conditions, ensuring that the chosen material can perform optimally in specific environments.

Related terms

Crystal Lattice: A systematic, repeating arrangement of atoms in a solid that defines its geometric structure.

Coordination Number:

The number of nearest neighbor atoms surrounding a central atom in a crystal structure.

Close-Packing: An arrangement of atoms that maximizes the density of the material, allowing for minimal empty space.