In which pair the percentage of void is lowest ?

Options

A. hcp and bcc
B. hcp and ccp
C. bcc and ccp
D. bcc and simple cubic cell.

Answer

To determine which pair has the lowest percentage of voids, we need to analyze the packing efficiency of different types of crystal structures. The percentage of voids can be calculated using the formula:

\[ \text{Percentage of void} = 100 - \text{Packing efficiency} \]

Let's evaluate the packing efficiencies for the given crystal structures:

1. **Hexagonal Close Packing (HCP)**:
- Packing Efficiency = 74%
- Percentage of void = \(100 - 74 = 26\%\)

2. **Body-Centered Cubic (BCC)**:
- Packing Efficiency = 68%
- Percentage of void = \(100 - 68 = 32\%\)

3. **Cubic Close Packing (CCP)**:
- Packing Efficiency = 74%
- Percentage of void = \(100 - 74 = 26\%\)

4. **Simple Cubic Cell (SCC)**:
- Packing Efficiency = 52.4%
- Percentage of void = \(100 - 52.4 = 47.6\%\)

Now, let's summarize the percentage of voids for each structure:

- HCP: 26%
- BCC: 32%
- CCP: 26%
- SCC: 47.6%

From this analysis, we can see that the lowest percentage of voids is found in both HCP and CCP, which is 26%.

Thus, the correct answer to the question is:

**HCP and CCP (Option 2)**