Question

In Silicon crystal, silicon atoms constitutes fcc where four out of 8 tetrahedral
holes are also occupied by Si atom. Calculate the total number of effective
atoms in a unit cell

1
2
4
8​

Answer 1

Answer:

For FCC = > no. of atoms => (1/8)*8 + 6*(1/2) => 4

plus the tetrahedral voids => 4

Hence total no. of atoms => 4 + 4 = 8

Answer 2

Given:

Silicon forms FCC lattice.

4 out of 8 tetrahedral  holes are also occupied by Si atom.

To Find:

The total number of effective  atoms in a unit cell of Silicon.

Calculation:

- For FCC lattice, the no of atoms per unit cell = 4

- The no of tetrahedral voids = 8

- The no of tetrahedral voids occupied by Si atoms = 4

- The total no of atoms per unit cell = 4 + 4 = 8

- So, the total number of effective  atoms in a unit cell of given Silicon crystal is Eight (8).