Face-centered cubic

Definition

Face-centered cubic (FCC) is a type of crystal structure where atoms are located at each of the corners and the centers of all the cube faces of the unit cell. This arrangement allows for a high packing efficiency, making it one of the most common structures in metals and some ionic compounds. FCC is notable for its symmetry and close packing, which influences the properties of materials that adopt this structure.

5 Must Know Facts For Your Next Test

1. The face-centered cubic structure has a coordination number of 12, meaning each atom is surrounded by 12 neighboring atoms.
2. Common metals with an FCC structure include aluminum, copper, gold, and silver, which contribute to their malleability and ductility.
3. FCC structures can exhibit slip systems that allow for easier deformation under stress, making these materials favorable in engineering applications.
4. The atomic packing factor (APF) for face-centered cubic structures is approximately 0.74, indicating that about 74% of the volume is occupied by atoms.
5. FCC structures often result in higher densities compared to other structures like body-centered cubic due to their efficient packing arrangement.

Review Questions

• How does the arrangement of atoms in a face-centered cubic structure influence its physical properties?
  • The arrangement of atoms in a face-centered cubic structure leads to high symmetry and efficient packing, which significantly affects physical properties such as density, strength, and ductility. The close-packed nature allows for more atoms to be present within a given volume, resulting in materials that are generally stronger and more resistant to deformation. Additionally, the coordination number of 12 in FCC contributes to its mechanical properties by enabling multiple slip systems for plastic deformation.
• Compare and contrast face-centered cubic structures with body-centered cubic structures in terms of coordination number and packing efficiency.
  • Face-centered cubic structures have a coordination number of 12 and a packing efficiency of about 74%, which means they can accommodate more atoms in a given space compared to body-centered cubic structures. In contrast, body-centered cubic structures have a coordination number of 8 and lower packing efficiency at around 68%. This difference affects their mechanical properties; FCC materials tend to be more malleable and ductile due to their higher packing density and available slip systems compared to BCC materials.
• Evaluate the role of face-centered cubic structures in the performance of metals used in engineering applications.
  • Face-centered cubic structures play a crucial role in the performance of various metals used in engineering applications due to their favorable mechanical properties. Metals like aluminum, copper, and gold exhibit FCC arrangements, allowing them to maintain strength while being highly ductile. This combination makes FCC metals ideal for manufacturing processes that require shaping or bending without breaking. Furthermore, the efficient atomic packing in FCC structures enhances their resistance to deformation under stress, making them reliable choices for construction and structural integrity in diverse engineering projects.

Related terms

Body-centered cubic: A crystal structure where atoms are located at each corner of a cube and a single atom is placed in the center of the cube.

Hexagonal close-packed: A crystal structure characterized by a hexagonal arrangement where atoms are closely packed in layers, offering similar packing efficiency to FCC.

Lattice: A three-dimensional arrangement of points representing the positions of atoms in a crystal structure.