What is the Difference Between FCC and HCP?
🆚 Go to Comparative Table 🆚The main difference between FCC (face-centered cubic) and HCP (hexagonal close-packed) structures lies in their packing arrangements and stacking sequences. Both FCC and HCP are close-packed structures, meaning they have the highest possible packing density for spheres in three dimensions. Here are the key differences between FCC and HCP:
- Packing Arrangement: FCC has a cubic close-packed structure, while HCP has a hexagonal close-packed structure.
- Coordination Number: In both FCC and HCP, each atom has a coordination number of 12, meaning each atom is in contact with 12 neighboring atoms.
- Number of Atoms per Unit Cell: FCC contains 4 atoms per unit cell, while HCP contains 6 atoms per unit cell.
- Stacking Sequence: In FCC, the third layer is different from the first layer, while in HCP, the third layer is similar to the first layer. The stacking sequence for FCC is ABC, while the stacking sequence for HCP is ABA.
Examples of metals with FCC structures include aluminum, copper, gold, lead, silver, and platinum. HCP structures are found in metals such as cobalt, cadmium, zinc, and the α phase of titanium.
Comparative Table: FCC vs HCP
The key difference between FCC (face-centered cubic) and HCP (hexagonal close-packed) structures is that FCC cycles among three layers, while HCP cycles among two layers. Here is a table comparing the two structures:
| Property | FCC | HCP |
|---|---|---|
| Lattice Structure | Face-centered cubic | Hexagonal close-packed |
| Layers | Cycles among three layers | Cycles among two layers |
| Stacking | Third layer is different from the first layer | Third layer is similar to the first layer (a-b-a-b-a-b) |
| Coordination Number | 12 | 12 |
| Atoms per Unit Cell | 4 | 6 |
Examples of metals with FCC structure include aluminum, copper, gold, lead, silver, and platinum, while examples of metals with HCP structure include cobalt, cadmium, zinc, and the α phase of titanium.