Lattice:HCP

HCP (Hexagonal close-packed) is a hexagonal lattice. It is notable (along with FCC) because it achieves the densest possible packing of spheres. It thus arises naturally in many atomic crystals, as well as in colloidal crystals and nanoparticles superlattices.

Canonical HCP

In the canonical HCP, the ratio between the a and c distances is:

${\frac {c}{a}}=2{\sqrt {\frac {2}{3}}}={\frac {2{\sqrt {6}}}{3}}\approx 1.633$

Examples

Elemental

4. Beryllium (Be) (a = b = 2.290 Å, c = 3.588, c/a = 1.567)

27. Cobalt (Co) (a = b = 2.5071 Å, c = 4.0695, c/a = 1.623)

48. Cadmium (Cd) (a =b = 2.9794 Å, c = 5.6186 Å, c/a = 1.886)

Atomic

• TBD

Nano

• Gold nanoparticles
  • Stoeva et al. Face-Centered Cubic and Hexagonal Closed-Packed Nanocrystal Superlattices of Gold Nanoparticles Prepared by Different Methods J. Phys. Chem. B 2003, 107 (30), 7441-7448 doi: 10.1021/jp030013+

See Also

• Wikipedia: Close-packing of equal spheres