# What is the total number of tetrahedral voids in FCC structure?

By Mandeep Kumar|Updated : September 27th, 2022

(a) 4

(b) 8

(c) 6

(d) 12

The total number of tetrahedral voids in FCC structure is 8. The atoms are positioned at the corners of the unit cell in a crystal structure. These are produced when the second layer of an atom is developed on top of the voids that its first layer has left behind.

### Tetrahedral Voids in FCC Structure

• Atoms can be found on the cube's faces.
• The atoms in the corner are divided across 8 cubes, with 18 contributions coming from each corner.
• The cube's corner has eight atoms in total.
• From each corner, total contribution = ⅛ x 8 = 1
• In a cube, contributions from the faces = 3
• Total atoms in an FCC structure = 4

Tetrahedral Voids

• Atoms positioned at the four corners of a typical tetrahedron help create it.
• Due to the presence of atoms on the lattice, there are twice as many tetrahedral voids.
• A total number of tetrahedral voids = 2 x the number of atoms per unit cell.
• As shown below, the cubic tight packing of the atoms forms a tetrahedral layer.
• The layers are arranged alternately, with the second layer occupying the depression left by the first layer.
• A tetrahedral void is indicated by the "T".
• In comparison to the size of the actual molecules, the hole or vacuum is minuscule.
• Tetrahedral voids have a coordination number of 4, and there are twice as many voids as atoms in each unit cell.
• Four atoms make up each unit cell of the FCC lattice.
• Total tetrahedral voids = 2 x the number of atoms per unit cell.
• Total tetrahedral voids = 2 x 4 = 8.
• As a result, the FCC structure contains a total of 8 tetrahedral voids.

Summary:

## What is the total number of tetrahedral voids in FCC structure? 4, 8, 6, 12

There are a total of 8 tetrahedral voids in the FCC structure. FCC stands for face centered cubic wherein atoms are arranged center of each cube face of the cell and at the corners.