Give packing efficiency and coordination number of the following crystal structures :
(a)body centred cubic (b)cubic close packing

Explanation

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

### Step 1: Understanding Body-Centered Cubic (BCC) Structure
- **Definition**: In a BCC structure, there is one atom at each corner of the cube and one atom at the center of the cube.
- **Coordination Number**: The coordination number is the number of nearest neighbors surrounding an atom. For BCC, each atom at the corners is surrounded by 8 atoms (the center atom and the 8 corner atoms). Thus, the coordination number for BCC is **8**.

### Step 2: Calculating Packing Efficiency for BCC
- **Volume of Atoms in BCC**: In a BCC unit cell, there are 2 atoms per unit cell (1 from the center and 1/8 from each of the 8 corners).
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