Hexagonal System

The hexagonal lattice is defined by a primary axis perpendicular to two base axes of equal length that intersect at a $120^\circ$ angle. This system serves as the foundation for the hexagonal close-packed (HCP) structure, one of the most efficient ways to pack spheres in a crystal.

Lattice parameters: $a = b \neq c$, and angles $\alpha = \beta = 90^\circ, \gamma = 120^\circ$.

Examples: Magnesium, Zinc, Titanium, and Graphite.