Question

What is void fraction in HCP unit cell?
68%
52%
26%
32%​

Answer 1

Answer:

26%

Explanation:

Hcp, Fcc, Ccp all have 74% packing efficiency.

So void % is 100-74, ie. 26%

.

Answer 2

To find:

Void fraction in HCP unit cell

Calculation:

HCP refers to Hexagonal Closed Packing.

In this type of lattices, the unit cell comprises of three layers of atoms.

The topmost and lowermost layer each consists of 6 atoms at the vertices of a hexagon and one atom at the centre.

The middle layer consists of three atoms arranged in a triangular fashion.

The packing fraction for HCP is highest amongst unit cells;

$\sf{packing \: fraction = 74\%}$

So, void fraction can be calculated by subtracting the packing fraction from 100%.

$\sf{void \: fraction = 100\% - 74\%}$

$\sf{ = > void \: fraction = 26\%}$

So, final answer is:

$\boxed{ \red{ \large {\sf{ void \: fraction = 26\%}}}}$