Cubic close-packed

Definition

Cubic close-packed (CCP) is a type of crystal structure where atoms are packed together efficiently in a three-dimensional arrangement, maximizing the density of the solid. In this arrangement, atoms are located at each corner of the cube and in the center of each face, resulting in a coordination number of 12, meaning each atom is in contact with 12 others. This structure plays a significant role in understanding how different materials behave and their properties in various applications.

5 Must Know Facts For Your Next Test

1. Cubic close-packed structures are commonly found in metals like copper, aluminum, and gold due to their high packing efficiency.
2. The unit cell of a cubic close-packed structure contains four atoms per cell, contributing to its dense arrangement.
3. Cubic close-packed structures exhibit strong metallic bonding, which contributes to properties like high electrical conductivity and malleability.
4. In cubic close-packed arrangements, the atomic radius can be related to the edge length of the cube through specific geometric relationships.
5. This structure is significant for understanding alloy formation, as many metallic alloys adopt a cubic close-packed arrangement for better stability.

Review Questions

• How does the atomic arrangement in cubic close-packed structures contribute to their high packing efficiency?
  • In cubic close-packed structures, atoms are arranged at the corners and centers of each face of the cube, which allows for efficient use of space. This arrangement results in a coordination number of 12, meaning that each atom is closely surrounded by 12 other atoms. The close proximity of the atoms maximizes the volume occupied by them, leading to higher density compared to other structures, making it highly efficient.
• Compare and contrast cubic close-packed structures with hexagonal close-packed structures regarding their atomic arrangements and properties.
  • Cubic close-packed and hexagonal close-packed structures both achieve high packing efficiency but differ in their geometrical arrangement. CCP has a cubic symmetry with layers arranged in an ABCABC pattern, while hexagonal close-packed has an ABAB pattern with alternating layers. Both structures have similar coordination numbers of 12, leading to comparable properties like strength and ductility; however, their distinct geometries can influence how they behave under stress and during alloy formation.
• Evaluate how the characteristics of cubic close-packed structures influence the mechanical properties of metals that adopt this arrangement.
  • Cubic close-packed structures enhance the mechanical properties of metals by providing high density and strong metallic bonding. The high coordination number contributes to improved ductility and malleability, allowing these metals to deform under stress without breaking. Additionally, the efficient atomic packing allows for better electron mobility, leading to higher electrical conductivity. These characteristics make CCP metals desirable for various industrial applications where strength and conductivity are critical.

Related terms

Face-centered cubic: A type of crystal structure similar to cubic close-packed where atoms are located at each corner and the centers of all faces of the cube.

Hexagonal close-packed: Another type of dense crystal structure that features layers of atoms arranged in a hexagonal pattern, resulting in high packing efficiency.

Coordination number: The number of nearest neighboring atoms surrounding a given atom in a crystal structure.