Cubic close-packed

Definition

Cubic close-packed (CCP) is a type of crystal structure characterized by a highly efficient arrangement of spheres, where each sphere is surrounded by twelve others in a repeating three-dimensional pattern. This arrangement maximizes the packing density, achieving about 74% efficiency in space utilization. The cubic close-packed structure is fundamental in understanding the properties and behaviors of many metallic and ionic compounds.

5 Must Know Facts For Your Next Test

1. Cubic close-packed structures are commonly found in metals such as copper, aluminum, and nickel, which display similar efficient packing properties.
2. In a cubic close-packed arrangement, layers of spheres alternate between two distinct orientations, often referred to as ABCABC stacking.
3. The coordination number in cubic close-packed structures is 12, meaning each atom is in contact with twelve neighboring atoms.
4. The face-centered cubic lattice can be described mathematically using the parameters of the unit cell, with atoms occupying specific positions within the cube.
5. Cubic close-packed structures can also relate to the concept of slip systems in materials science, which influences ductility and malleability in metals.

Review Questions

• How does the cubic close-packed structure compare to other crystal structures in terms of packing efficiency?
  • Cubic close-packed structures are one of the most efficient arrangements for packing spheres, achieving about 74% packing efficiency. Compared to other structures like body-centered cubic or simple cubic, which have lower packing efficiencies (68% and 52% respectively), CCP offers a denser configuration. The efficiency stems from its arrangement where each atom touches twelve others, optimizing space utilization within a unit cell.
• Describe how the atomic radius affects the formation and stability of cubic close-packed structures.
  • The atomic radius plays a crucial role in determining how closely atoms can pack together in a cubic close-packed structure. A smaller atomic radius allows for tighter packing, leading to a more stable arrangement. When atoms have similar sizes and radii, they can effectively occupy positions in the crystal lattice without leaving significant voids. If there's a significant difference in atomic radii, it can disrupt this close packing and lead to different structural arrangements.
• Evaluate the significance of cubic close-packed structures in industrial applications and material properties.
  • Cubic close-packed structures are vital in various industrial applications due to their impact on material properties like strength and ductility. Metals such as copper and aluminum, which exhibit CCP arrangements, are used extensively in construction and manufacturing due to their ability to deform under stress without breaking. Understanding CCP helps engineers design materials with desirable mechanical properties for specific applications, influencing everything from aerospace engineering to electronics.

Related terms

Face-centered cubic: A crystal structure where atoms are located at each of the corners and the centers of all the faces of the cube, similar to cubic close-packed but with different packing arrangements.

Hexagonal close-packed: A crystal structure where spheres are packed closely together in a hexagonal arrangement, which is another efficient packing method alongside cubic close-packed.

Atomic radius: The distance from the nucleus of an atom to the boundary of its surrounding cloud of electrons, influencing how atoms pack together in different structures.