Given packing efficiency and coordination number of the following crystal structres .
(a) body centred cubic (b) cubic close packing

Explanation

To find the packing efficiency and coordination number of the body-centered cubic (BCC) and cubic close packing (CCP) structures, we can follow these steps:

### Step 1: Body-Centered Cubic (BCC)

1. **Define the Structure**: In a body-centered cubic structure, there is one atom at each corner of the cube and one atom at the center of the cube.

2. **Coordination Number**: The coordination number is the number of nearest neighbors surrounding an atom. In BCC, each atom at the center is surrounded by 8 corner atoms. Therefore, the coordination number for BCC is **8**.

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