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 faces of the cube. This arrangement leads to high packing efficiency and stability, making it a common structure for many metals. The unique positioning of atoms in this structure plays a crucial role in the overall characteristics of crystal systems, atomic packing, and unit cell types.

5 Must Know Facts For Your Next Test

1. The face-centered cubic structure has a coordination number of 12, meaning each atom is in contact with 12 neighboring atoms.
2. FCC has an atomic packing factor (APF) of 0.74, indicating that 74% of the volume is occupied by atoms, making it one of the most efficient packing arrangements.
3. Common metals that adopt the FCC structure include aluminum, copper, gold, and silver due to their close-packed nature and favorable physical properties.
4. The unit cell of an FCC lattice contains four atoms, calculated as one atom from each of the eight corners (1/8 * 8 = 1) plus one atom from each of the six faces (1/2 * 6 = 3), totaling 4.
5. FCC structures exhibit high ductility and malleability, which allows them to be easily shaped without breaking, making them ideal for various applications in engineering and manufacturing.

Review Questions

• How does the face-centered cubic structure contribute to the physical properties of metals?
  • The face-centered cubic structure allows metals to achieve high packing efficiency due to its coordination number of 12 and atomic packing factor of 0.74. This arrangement enhances metallic bonding and results in improved ductility and malleability, enabling metals like copper and aluminum to be easily formed into various shapes without fracturing. The close proximity of atoms in FCC also contributes to higher strength and stability under stress.
• Compare the face-centered cubic structure with the body-centered cubic structure regarding atomic arrangement and properties.
  • The face-centered cubic structure has atoms located at the corners and centers of each face of the cube, leading to a total of four atoms per unit cell and a higher coordination number of 12. In contrast, the body-centered cubic structure contains one atom at each corner and one atom at the center, totaling two atoms per unit cell with a lower coordination number of 8. As a result, FCC generally exhibits superior ductility and strength compared to BCC due to its more efficient atomic packing.
• Evaluate how the face-centered cubic structure influences alloy formation and material performance in engineering applications.
  • The face-centered cubic structure plays a significant role in alloy formation as it allows for interstitial solutions where smaller atoms can fit between larger FCC atoms without significantly disrupting the lattice. This property is essential for enhancing material performance by improving mechanical strength and corrosion resistance. Engineers leverage FCC's ductility and high packing efficiency to design alloys that can withstand various stresses in applications like aerospace and automotive industries, ensuring durability while maintaining lightweight characteristics.

Related terms

Close packing: An efficient arrangement of atoms in a crystal where they occupy the minimum amount of space, maximizing density.

Hexagonal close-packed: A crystal structure similar to FCC but with a different arrangement of layers, allowing for tight packing of atoms.

Body-centered cubic: A type of crystal structure where atoms are positioned at each corner of the cube and a single atom is located at the center, offering different packing and properties compared to FCC.