`26%` void space in its crystal structure is obsered for
A) FCC structure
B) HCP structure
C) CCP structure

Options

A. A only
B. B only
C. C only
D. All A, B, C

Answer

To solve the question regarding the void space in crystal structures, we will analyze the packing efficiency of the given structures: FCC (Face-Centered Cubic), HCP (Hexagonal Close-Packed), and CCP (Cubic Close-Packed).

### Step-by-Step Solution:

1. **Understanding the Structures**:
- **FCC Structure**: In an FCC structure, there are atoms located at each of the corners and the centers of each face of the cube.
- **HCP Structure**: The HCP structure consists of two layers of atoms arranged in a hexagonal pattern, with the layers stacked in an ABAB pattern.
- **CCP Structure**: The CCP structure is similar to FCC but is defined by an ABCABC stacking sequence.

2. **Calculating Number of Atoms per Unit Cell**:
- For **FCC**:
- There are 8 corner atoms, each contributing \( \frac{1}{8} \) of an atom, and 6 face-centered atoms, each contributing \( \frac{1}{2} \).
- Total atoms = \( 8 \times \frac{1}{8} + 6 \times \frac{1}{2} = 1 + 3 = 4 \) atoms per unit cell.
- For **HCP**:
- The number of atoms in HCP is also 6 (2 in the top layer and 4 in the bottom layer).
- For **CCP**:
- The number of atoms in CCP is the same as FCC, which is 4 atoms per unit cell.

3. **Calculating Packing Efficiency**:
- The packing efficiency (PE) can be calculated using the formula:
\[ \text{Packing Efficiency} = \frac{z \times \text{Volume of one atom}}{\text{Volume of unit cell}} \times 100 \]
- For FCC and CCP, the packing efficiency is approximately 74%, leading to a void space of:
\[ \text{Void Space} = 100\% - \text{Packing Efficiency} = 100\% - 74\% = 26\% \]
- For HCP, the packing efficiency is also around 74%, resulting in the same void space of 26%.

4. **Conclusion**:
- All three structures (FCC, HCP, and CCP) have a void space of 26%. Therefore, the correct answer to the question is that all the given structures exhibit 26% void space.

### Final Answer:
**All of the above (FCC, HCP, CCP) have 26% void space.**