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.

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