Question

The right option for the number of tetrahedral and octahedral voids in the hexagonal primitive unit cell is ______.

Options

• 6, 12

• 2, 1

• 12, 6

• 8, 4

Answer 1

The right option for the number of tetrahedral and octahedral  voids in the hexagonal primitive unit cell is 12, 6.

Explanation:

In hexagonal close-packed (hcp) structure, each unit cell contains 6 atoms.

Octahedral voids form at positions where six spheres surround a space.

The number of octahedral voids = number of atoms in the unit cell.

Tetrahedral voids are smaller spaces surrounded by four atoms.

There are 2 tetrahedral voids per atom.

So 6 atoms × 2 = 12 tetrahedral voids.